MAGNETIC CRASH SENSOR
A magnetic field is generated by at least one coil in magnetic communication with at least a portion of a vehicle responsive to a first time-varying signal operatively coupled to the at least one coil in series with a sense resistor. A second signal is generated responsive to a voltage across the sense resistor and is response to a magnetic condition of the at least one coil, which is response to the magnetic communication of the at least one coil with the portion of the vehicle.
Latest TK HOLDINGS, INC. Patents:
The instant application is a continuation-in-part of application Ser. No. 11/932,439 (“Application '439”) filed on Oct. 31, 2007, which is a continuation-in-part of International Application Serial No. PCT/US06/62055 filed on Dec. 13, 2006, which is a continuation-in-part of U.S. application Ser. No. 11/530,492 (“Application '492”) filed on Sep. 11, 2006, and which claims benefit of U.S. Provisional Application Ser. Nos. 60/750,122 filed on Dec. 13, 2005. Application '492 is a continuation-in-part of U.S. application Ser. No. 10/946,174 filed on Sep. 20, 2004, now U.S. Pat. No. 7,209,844, which issued on 24 Apr. 2007, and which claims the benefit of prior U.S. Provisional Application Ser. No. 60/504,581 filed on Sep. 19, 2003. Application '492 is also a continuation-in-part of U.S. application Ser. No. 10/905,219 filed on Dec. 21, 2004, now U.S. Pat. No. 7,212,895, which issued on 1 May 2007, and which claims the benefit of prior U.S. Provisional Application Ser. No. 60/481,821 filed on Dec. 21, 2003. Application '492 is also a continuation-in-part of U.S. application Ser. No. 11/460,982 filed on Jul. 29, 2006, which claims the benefit of prior U.S. Provisional Application Ser. No. 60/595,718 filed on Jul. 29, 2005. Application '439 also claims the benefit of U.S. Provisional Application Ser. No. 60/892,241 filed on Feb. 28, 2007. The instant application is also a continuation-in-part of U.S. application Ser. No. 11/685,624 filed on Mar. 13, 2007, which is a continuation-in-part of U.S. application Ser. No. 10/666,165 filed on Sep. 19, 2003, now U.S. Pat. No. 7,190,161, which is a continuation-in-part of U.S. application Ser. No. 09/649,416 filed on Aug. 26, 2000, now U.S. Pat. No. 6,777,927, which claims the benefit of prior U.S. Provisional Application Ser. No. 60/151,220 filed on Aug. 26, 1999, and which claims the benefit of prior U.S. Provisional Application Ser. No. 60/151,424 filed on Aug. 26, 1999. Each of the above-identified applications is incorporated by reference in its entirety.
BRIEF DESCRIPTION OF THE DRAWINGSIn the accompanying drawings:
Referring to
The magnetic crash sensor 10.1 further comprises at least one magnetic sensor 36 that is located separate from the at least one first coil 14, and which is adapted to be responsive to the first magnetic field 26 generated by the at least one first coil 14 and to be responsive to a second magnetic field 38 generated by the eddy currents 34 in the conductive element 18 responsive to the first magnetic field 26. For example, the sensitive axis of the at least one magnetic sensor 36 is oriented in substantially the same direction as the magnetic axis 32 of the at least one first coil 14. For example, as illustrated in
Referring to
The first aspect of the magnetic crash sensor 10.1 provides for monitoring the shape and position of a front member of a vehicle, such as the bumper, so as to provide early warning for significant energy impacts. The magnetic crash sensor 10.1 could also provide a signal from which impacts with pedestrians can be identified and potentially differentiated from those with other low mass or unfixed objects. For example, a signal responsive to either the first 36.1 or second 36.2 magnetic sensors could be used to actuate pedestrian protection devices; to actuate resettable vehicle passenger restraint devices (e.g. mechanical seatbelt pretensioners); or to alert a frontal crash detection algorithm that a crash is beginning, wherein, for example, the frontal crash detection algorithm might adapt one or more thresholds responsive thereto. The dynamic magnitude of the signal from the magnetic sensor 36 provides a measure of crash severity.
The first aspect of the magnetic crash sensor 10.1 is useful for sensing impacts to elements of the vehicle 12 that are either non-structural or which are readily deformed responsive to a crash. Changes in elements of which the conductive element 18 is either operatively associated or at least a part of cause an associated influence of the associated magnetic field. This influence occurs at the speed of light. Furthermore, direct structural contact between the impacted element—i.e. the conductive element 18—and the associated sensing system—i.e. the at least one first coil 14 and magnetic sensor 36—is not required as would be the case for a crash sensing system dependent upon either an accelerometer or a magnetostrictive sensor, because the first aspect of the magnetic crash sensor 10.1 is responsive to changes in the geometry of the region covered by the magnetic fields associated therewith, which includes the space between the conductive element 18 and the associated at least one first coil 14 and magnetic sensor 36. The responsiveness of the first aspect of the magnetic crash sensor 10.1 is improved if these elements are located so that a nonmagnetic material gap in the associated magnetic circuit is either increased or decreased responsive to a crash, thereby affecting the overall reluctance of the associated magnetic circuit, and as a result, affecting the resulting signal sensed by the magnetic sensor 36.
The first aspect of the magnetic crash sensor 10.1 is well suited for detecting impacts to non-ferrous elements of the vehicle 12. For example, for elements that are poor conductors, the conductive element 18 operatively associated therewith provides for detecting deformations thereof. As another example, for elements that are good conductors, e.g. aluminum bumpers or body panels, those elements inherently comprise the conductive element 18 of the magnetic crash sensor 10.1.
A conductive element 18 could also be added to a ferrous element, e.g. a steel bumper, in accordance with the first aspect of the magnetic crash sensor 10.1, although in order for the effect of the second magnetic field 38 to dominate an effect of a magnetic field within the ferrous element, the associated conductive element 18 on the inside of the ferrous element (steel bumper) would need to be thick enough or conductive enough to prevent the original transmitted first magnetic field 26 from penetrating though to the steel on the other side of the conductive element 18, whereby eddy currents 34 in the conductive element 18 would substantially cancel the magnetic field at some depth of penetration into the conductive element 18 for a sufficiently thick, sufficiently conductive conductive element 18. For example, for a superconducting conductive element 18, there would be no penetration of the first magnetic field 26 into the conductive element 18. Although the depth of penetration of the first magnetic field 26 increases as the conductivity of the conductive element 18 decreases, an aluminum or copper conductive element 18 would not need to be very thick (e.g. 2 mm or less) in order to substantially achieve this effect. The depth of penetration of magnetic fields into conductive elements is known from the art using eddy currents for non-destructive testing, for example, as described in the technical paper eddyc.pdf available from the internet at http://joe.buckley.net/papers, which technical paper is incorporated herein by reference. Generally, if the thickness of the conductive element 18 exceeds about three (3) standard depths of penetration at the magnetic field frequency, then substantially no magnetic field will transmit therethrough.
Alternatively, in the case of ferromagnetic element, e.g. a steel bumper, a magnetic crash sensor could be constructed as described hereinabove, except without a separate conductive element 18, i.e. separate from the ferromagnetic element which is itself conductive. Accordingly, the first magnetic field 26 would be conducted through this ferromagnetic element second portion 20 of the vehicle 12, which is part of a magnetic circuit further comprising the at least one first coil 14, the first portion 16 of the vehicle 12, and the associated air gaps 48 between the first 16 and second 20 portions of the vehicle 12. In accordance with this aspect, the magnetic sensor 36 would be responsive to changes in the reluctance of the magnetic circuit caused by deformation or translation of the ferromagnetic first portion 16 of the vehicle 12, and by resulting changes in the associated air gaps 48.
Referring to
The magnetic crash sensor 10.2 further comprises at least one magnetic sensor 62 that is located separate from the at least one second coil 50, and which is adapted to be responsive to the third magnetic field 54 generated by the at least one second coil 50 and conducted through the frame 64 of the vehicle 12 For example, as illustrated in
The third magnetic field 54 is conducted through a magnetic circuit 68 comprising the above described elements of the frame 64 of the vehicle 12, and which may further comprise elements of the body or powertrain, or other associated structural elements, particularly elements comprising ferromagnetic materials. The responsiveness of the second aspect of the magnetic crash sensor 10.2 can be enhanced if the associated magnetic circuit 68 comprises one or more gaps 70 comprising non-magnetic material, the separation thereof which is responsive to a crash to be sensed by the magnetic crash sensor 10.2, thereby modulating the associated reluctance of the magnetic circuit 68 responsive to the crash. For example, the one or more gaps 70 could comprise a structural nonferrous material, such as aluminum or structural plastic of the frame 64 of the vehicle 12, which is adapted to be either compressed or stretched responsive to the crash, causing the associated reluctance of the magnetic circuit 68 to either decrease or increase respectively.
The second aspect of the magnetic crash sensor 10.2 provides for monitoring damage to the structure of the vehicle 12 responsive to crashes involving a substantial amount of associated inelastic deformation. Referring to
Generally, during major crash events where deployment of the safety restraint actuator 44 is desired, significant associated damage and associated metal bending generally occurs to vehicle structures rearward of the front bumper region. After the impacting object 46 has been detected by the first embodiment of the first aspect of the magnetic crash sensor 10.1 as described hereinabove, the vehicle crush zone and crush pattern will generally either be limited to primarily the bumper region or will extend further into the vehicle, impacting one or more major vehicle structural members. If the object intrusion is limited primarily to the bumper or hood region, then a crash would likely be detected only by the first aspect of the magnetic crash sensor 10.1. However, if the impacting object 46 intrudes on a major structural member, then a significant signal change is detected by the third 62.1 and fourth 62.2 magnetic sensors of the second embodiment of the magnetic crash sensor 10.2 responsive to a deformation of the frame 64 of the vehicle 12. The signature of the signal(s) from either of the third 62.1 and fourth 62.2 magnetic sensors, i.e. the associated magnitude and rate of change thereof, can be correlated with impact severity and can be used to actuate one or more safety restraint actuators 44 appropriate for the particular crash. Accordingly, in combination, the first 10.1 and second 10.2 aspects of the magnetic crash sensor provide for faster and better crash discrimination, so as to provide for either actuating or suppressing actuation of the associated safety restraint actuators 44. Furthermore, the affects of a crash on the magnetic circuits of either the first 10.1 or second 10.2 aspects of the magnetic crash sensor are propagated to the respective magnetic sensors 26, 62 at the speed of light, and accordingly is not limited by the speed with which shock waves propagate through the associated structural elements, as would be the case for either accelerometer or magnetostrictive sensing technologies. Furthermore, in combination, the first 10.1 and second 10.2 aspects of the magnetic crash sensor provide for detecting and differentiating various types of frontal impacts, including but not limited to, impacts with pedestrians, other vehicles, fixed objects or other objects, so as to further provide for deploying safety measures that are appropriate to the particular situation, and responsive to the predicted type of impacting object and the detected severity of the impact. Furthermore, the first 10.1 and second 10.2 aspects of the magnetic crash sensor, provide for relatively fast detection of collisions, differentiation between events requiring the actuation of a safety restraint actuator 44 from those for which the actuation thereof should be suppressed, and determination of the location, extent and energy of the collision from the information of the collision that can be detected using the signals from the associated magnetic sensors 26, 62 responsive to the associated magnetic fields 26, 38, 54 of the magnetic crash sensors 10.1, 10.2.
Referring to
The at least one coil 14, 72 is electrically conductive and is adapted for generating a first magnetic field 94 responsive to a current applied by a coil driver 96, e.g. responsive to a first oscillatory signal generated by an oscillator 98. The magnetic axis 100 of the at least one coil 14, 72 is oriented towards the second portion 82 of the door 78—e.g. towards the outer skin 90 of the door 78, e.g. substantially along the lateral axis of the vehicle for the embodiment illustrated in FIGS. 6 and 7—so that the first magnetic field 94 interacts with the conductive elements 86, 88 operatively associated therewith, thereby causing eddy currents 102 to be generated therein in accordance Lenz's Law. The conductive elements 86, 88 each comprise, for example, a thin metal sheet, film or coating, comprising either a paramagnetic or diamagnetic material that is relatively highly conductive, e.g. aluminum or copper, and which, for example, could be an integral part of the second portion 82 of the door 78. For example, the conductive elements 86, 88 could be in the form of relatively thin plates, a film, or a coating that is mounted on, applied to, or integrated with existing or supplemental structures associated with the door beam 92 and the inside surface of the outer skin 90 of the door 78 respectively. The frequency of the oscillator 98 is adapted so that the corresponding oscillating magnetic field generated by the at least one coil 14, 72 both provides for generating the associated eddy currents 102 in the conductive elements 86, 88, and is magnetically conducted through the ferromagnetic elements of the door 78 and proximate structure of the vehicle 12.
The at least one magnetic sensor 74 is located separate from the at least one coil 14, 72, and is adapted to be responsive to the first magnetic field 94 generated by the at least one coil 14, 72 and to be responsive to a second magnetic field 104 generated by the eddy currents 102 in the conductive elements 86, 88 responsive to the first magnetic field 94. For example, the sensitive axis of the at least one magnetic sensor 74 is oriented in substantially the same direction as the magnetic axis 100 of the at least one coil 14, 72. The magnetic sensor 74 generates a signal responsive to a magnetic field, and can be embodied in a variety of ways, for example, including, but not limited to, a coil, a Hall-effect sensor, or a giant magnetoresistive (GMR) sensor. The number of magnetic sensors 74 and the spacing and positioning thereof on the inner panel 84 of the door 78 is dependent upon the vehicle 12, the type of performance required, and associated cost constraints. Generally, more magnetic sensors 74 would possibly provide higher resolution and faster detection speed, but at increased system cost. Increasing either the vertical or fore/aft spacing between two or more magnetic sensors 74 reduces associated coupling with the first magnetic field 94, increases coupling with the second magnetic field 104, and provides for a more general or average indication of electrically conductive element movement during a crash, potentially slowing the ultimate detection response, but increasing immunity to false positive crash detections, i.e. immunity to non-crash events. With only one coil 14, 72 and one magnetic sensor 74, it may be beneficial to provide a separation thereof of about ¼ to ⅓ the length of a major diagonal though the cavity within the door 78.
The at least one magnetic sensor 74 is operatively coupled to a respective signal conditioner/preprocessor circuit 106, which, for example, provide for preamplification, filtering, synchronous demodulation, and analog to digital conversion of the associated signals from the at least one magnetic sensor 74, e.g. as described in U.S. Pat. No. 6,777,927, which is incorporated herein by reference. The signal conditioner/preprocessor circuit 106 is operatively coupled to a processor 108 which processes the signal therefrom, thereby providing for discriminating a crash, and controlling an associated safety restraint actuator 110—e.g. a side air bag inflator—operatively coupled thereto.
In operation, the magnetic crash sensor 10.1′ provides a measure of the relative motion of either the outer skin 90 or the door beam 92 relative to the inner panel 84 of the door 78, for example, as caused by a crushing or bending of the door 78 responsive to a side-impact of the vehicle 12. During non-crash conditions, an oscillating magnetic field resulting from the combination of the first 94 and second 104 magnetic fields would be sensed by the at least one magnetic sensor 74. If an object impacted the outer skin 90 of the door 78 causing a physical deflection thereof, then this oscillating magnetic field would be perturbed at least in part by changes in the second magnetic field 104 caused by movement or deformation of the associated first conductive element 86 and the associated changes in the associated eddy currents 102 therein. If the impact is of sufficient severity, then the door beam 92 and the associated second conductive element 88 would also be moved or deformed thereby, causing additional and more substantial changes in the associated eddy currents 102 in the second conductive element 88 and the corresponding second magnetic field 104. Generally, the door beam 92 and associated second conductive element 88 would either not be significantly perturbed or would only be perturbed at a reduced rate of speed during impacts that are not of sufficient severity to warrant deployment of the associated safety restraint actuator 110, notwithstanding that there may be substantial associated deformation of the outer skin 90 of the door 78. Accordingly, in a magnetic crash sensor 10.1′ incorporating only a single conductive element 80, a preferred location thereof would be that of the second conductive element 88 described hereinabove.
In accordance with another embodiment, an accelerometer 112, or another crash sensor, could be used in combination with the above-described magnetic crash sensor 10.1′ in order to improve reliability by providing a separate confirmation of the occurrence of an associated crash, which may be useful in crashes for which there is not a significant deflection of either the outer skin 90 of the door 78, or of the door beam 92, relatively early in the crash event—for example, as a result of a pole impact centered on the B-pillar or a broad barrier type impact that spans across and beyond the door 78—for which the magnetic crash sensor 10.1′, if used alone, might otherwise experience a delay in detecting the crash event. For example, a supplemental accelerometer 112 might be located at the base of the B-pillar of the vehicle 12. As another example, an additional supplemental accelerometer 112 might be located proximate to the safety restraint actuator 110. In a system for which the magnetic crash sensor 10.1′ is supplemented with a separate crash sensor, e.g. an accelerometer 112, the safety restraint actuator 110 would be deployed either if the magnetic crash sensor 10.1′ detected a significant and relatively rapid change in the magnetic field in combination with the acceleration exceeding a relatively low threshold, or if the accelerometer 112 detected a significant and relatively rapid change in acceleration in combination with the magnetic crash sensor 10.1′ detecting at least a relatively less significant and relatively less rapid change in the magnetic field.
It should be understood, that the performance of a coil used for either generating or sensing a magnetic field may sometimes be enhanced by the incorporation of an associated magnetic core of relatively high magnetic permeability. Furthermore, it should be understood that the signal applied to either the at least one first coil 14, second coil 50 or of coil 14, 72 could be a direct current signal so as to create a steady magnetic field. Alternatively, those coils could be replaced with corresponding permanent magnets, whereby the associated magnetic crash sensors 10.1, 10.1′ or 10.2 would then be responsive to transients in the magnetic fields responsive to an associated crash. Furthermore, it should be understood that the particular oscillatory waveform of the first oscillator 30, second oscillator 58 or oscillator 98 is not limiting, and could be, for example, a sine wave, a square wave, a sawtooth wave, or some other waveform; of a single frequency, or of plural frequencies that are either stepped or continuously varied.
Referring to
The at least one first coil 14 is operatively coupled to a signal conditioner/preprocessor circuit 114.1 which, for example, provides for preamplification, filtering, synchronous demodulation and analog to digital conversion of the associated signal from the at least one first coil 14. The signal conditioner/preprocessor circuit 114.1 is operatively coupled to a processor 116 which processes the signals therefrom, thereby providing for discriminating a crash, and controlling an associated safety restraint actuator 44—e.g. a frontal air bag inflator or a seat belt pretensioner—operatively coupled thereto. More particularly, the processor 116 provides for determining a measure responsive to the self-impedance of the at least one first coil 14 responsive to an analysis of the complex magnitude of the signal from the at least one first coil 14, for example, in relation to the signal applied thereto by the associated oscillator 30.
Responsive to a crash with an impacting object 46 (e.g. as illustrated in
The decomposition of a signal into corresponding real and imaginary components is well known in the art, and may be accomplished using analog circuitry, digital circuitry or by software or a combination thereof. For example, U.S. Pat. Nos. 4,630,229, 6,005,392 and 6,288,536—all of which is incorporated by reference herein in their entirety—each disclose various systems and methods for calculating in real-time the real and imaginary components of a signal which can be used for processing the signal from the at least one first coil 14. A Maxwell-Wien bridge, e.g. incorporated in the signal conditioner/preprocessor circuit 114.1, may also be used to determine the real and imaginary components of a signal, or a phase-locked loop may be used to determine the relative phase of a signal with respect to a corresponding signal source, which then provides for determining the associated real and imaginary components. Various techniques known from the field eddy current inspection can also be used for processing the signal from the at least one first coil 14, for example, as disclosed in the Internet web pages at http://www.ndt-ed.org/EducationResources/CommunityCollege/EddyCurrents/cc_ec_index.htm, which are incorporated herein by reference. The magnetic sensor 10 can employ various signal processing methods to improve performance, for example, multiple frequency, frequency hopping, spread spectrum, amplitude demodulation, phase demodulation, frequency demodulation, etc.
A signal responsive to the self-impedance of the at least one first coil 14—e.g. responsive to the real and imaginary components of the signal from the one first coil 14—is processed by a crash sensing algorithm in the processor 116—e.g. by comparison with a threshold or with a reference signal or waveform—and if a crash is detected thereby, e.g. a crash of sufficient severity, then the processor 42 provides for either activating the safety restraint actuator 44 responsive thereto, or provides for activation thereof responsive to a second confirmatory signal from a second crash sensor.
Referring to
The at least one second coil 50 is operatively coupled to a signal conditioner/preprocessor circuit 114.2 which, for example, provides for preamplification, filtering, synchronous demodulation and analog to digital conversion of the associated signal from the at least one second coil 50. The signal conditioner/preprocessor circuit 114.2 is operatively coupled to a processor 116 which processes the signals therefrom, thereby providing for discriminating a crash, and controlling an associated safety restraint actuator 44—e.g. a frontal air bag inflator or a seat belt pretensioner—operatively coupled thereto. More particularly, the processor 116 provides for determining a measure responsive to the self-impedance of the at least one second coil 50 responsive to an analysis of the complex magnitude of the signal from the at least one second coil 50, for example, in relation to the signal applied thereto by the associated oscillator 58.
The third magnetic field 54 is conducted through a magnetic circuit 68 comprising the above described elements of the frame 64 of the vehicle 12, and which may further comprise elements of the body or powertrain, or other associated structural elements, particularly elements comprising ferromagnetic materials. The responsiveness of the second aspect of the magnetic crash sensor 10.2′ can be enhanced if the associated magnetic circuit 68 comprises one or more gaps 70 comprising non-magnetic material, the separation thereof which is responsive to a crash to be sensed by the magnetic crash sensor 10.2′, thereby modulating the associated reluctance of the magnetic circuit 68 responsive to the crash. For example, the one or more gaps 70 could comprise a structural nonferrous material, such as aluminum or structural plastic of the frame 64 of the vehicle 12, which is adapted to be either compressed or stretched responsive to the crash, causing the associated reluctance of the magnetic circuit 68 to either decrease or increase respectively.
The signal conditioner/preprocessor circuit 114.2 provides for measuring the signal across the at least one second coil 50 and provides for measuring the signal applied thereto by the associated coil driver 56. The signal conditioner/preprocessor circuit 114.2—alone, or in combination with the processor 116, provides for decomposing the signal from the at least one second coil 50 into real and imaginary components, for example, using the signal applied by the associated oscillator 58 as a phase reference. A signal responsive to the self-impedance of the at least one second coil 50—e.g. responsive to the real and imaginary components of the signal from the one second coil 50—is processed by a crash sensing algorithm in the processor 116—e.g. by comparison with a threshold or with a reference signal or waveform—and if a crash is detected thereby, e.g. a crash of sufficient severity, then the processor 42 provides for either activating the safety restraint actuator 44 responsive thereto, or provides for activation thereof responsive to a second confirmatory signal from a second crash sensor.
It should be understood that the third embodiment of a first aspect of a magnetic crash sensor 10.1″ and the second embodiment of a second aspect of a magnetic crash sensor 10.2′ may be used either in combination—as illustrated in
Referring to
The at least one coil 14, 72 is electrically conductive and is adapted for generating a first magnetic field 94 responsive to a current applied by a coil driver 96, e.g. responsive to a first oscillatory signal generated by an oscillator 98. The magnetic axis 100 of the at least one coil 14, 72 is oriented towards the second portion 82 of the door 78—e.g. towards the outer skin 90 of the door 78, e.g. substantially along the lateral axis of the vehicle for the embodiment illustrated in FIGS. 9 and 10—so that the first magnetic field 94 interacts with the conductive elements 86, 88 operatively associated therewith, thereby causing eddy currents 102 to be generated therein in accordance Lenz's Law. For example, the at least one coil 14, 72 may comprise a coil of wire of one or more turns, or at least a substantial portion of a turn, wherein the shape of the coil 14, 72 is not limiting, and may for example be circular, elliptical, rectangular, polygonal, or any production intent shape. For example, the coil 14, 72 may be wound on a bobbin, and, for example, sealed or encapsulated, for example, with a plastic or elastomeric compound adapted to provide for environmental protection and structural integrity. The resulting coil assembly may further include a connector integrally assembled, e.g. molded, therewith. Alternatively, the at least one coil 14, 72 may be formed by wire bonding, wherein the associated plastic coating is applied during the associated coil winding process.
In one embodiment, the size and shape of the coil 14, 72 are adapted so that the induced first magnetic field 94 covers the widest portion of the door 78. In another embodiment, depending on door 78 structural response, this coverage area can be reduced or shaped to best respond to an intruding metal responsive to a crash. For example, a CAE (Computer Aided Engineering) analysis involving both crash structural dynamics and/or electromagnetic CAE can be utilized to determine or optimized the size, shape, thickness—i.e. geometry—of the coil 14, 72 that both satisfies associated packaging requirements within the door 78 and provides sufficient crash detection capability.
For example, in one embodiment, an assembly comprising the at least one coil 14, 72 is positioned within the door 78 of the vehicle 12 so that the magnetic axis 100 of the at least one coil 14, 72 is substantially perpendicular to the outer skin 90 of the door 78, wherein the outer skin 90 is used as an associated sensing surface. Alternatively, the mounting angle relative to the outer skin 90 may be optimized to account for the shape of the associated metal surface and the relative proximity an influence of an associated door beam 92 or other structural elements relative to the outer skin 90. The position of the coil 14, 72 may be chosen so that the coil 14, 72 is responsive to structures, structural elements or body elements that typically intrude relative to an occupant responsive to a crash, so as to provide for optimizing responsiveness to a measure of crash intrusion for ON crashes, while also providing for sufficient immunity to OFF crashes, for both regulatory and real world crash modes. For example, the coil 14, 72 within the door 78 could be adapted to be responsive to the outer skin 90, a conductive element 80, 86 operatively associated therewith, a door beam 92, a conductive element 80, 88 operatively associated therewith, or an edge wall 118 of the door 78, either individually or in combination.
The position, size, thickness of the chosen sensor coil 14, 72 are selected to fit within the mechanical constraints of and within the door 78 associated with electrical or mechanical functions such as window movement, door 78 locks, etc. For example, in accordance with one embodiment, the coil 14, 72 is affixed to an inner portion of the door 78, for example, through rigid and reliable attachment to an inner panel 84 of the door 78b, so as to reduce or minimize vibration of the coil 14, 72 relative to the associated conductive element 80 being sensed (e.g. a metallic outer skin 90 of the door 78). For example, in accordance with another embodiment, the sensing coil 14, 72 could molded into an inner panel 84 of the door 78 during the manufacturing of the door 78, and/or the inner panel 84 could be adapted to provide for a snap insert for the sensing coil 14, 72 therein.
For a coil 14, 72 mounted within the door 78, the coil 14, 72 position/location may be chosen such that any conductive and/or ferromagnetic structural or body elements proximate to the inside side of the coil 14, 72 are relatively rigidly fixed so as reduce electromagnetic influences of these elements on the coil 14, 72, thereby emphasizing an influence of a crash intrusion from the exterior side of the door 78. Accordingly, it is beneficial for the coil 14, 72 to be relatively rigidly mounted to within the vehicle 12 so that the amount of relative motion between the coil 14, 72 and any nearby conductive materials is limited when actual metal deformation/intrusion does not occur, for example, as a result of vibration, particularly for conductive materials within about one coil radius of the coil 14, 72.
The coil 14, 72 would be mounted so as to be responsive to the surface being sensed or monitored. For example, in one embodiment, the coil 14, 72 is mounted a distance within about one coil 14, 72 radius (e.g. for a circular coil 14, 72) away from the outer skin 90 or target conductive element 80, 86, 88 to be monitored. The coil 14, 72 does not require any particular shape, and regardless of the shape, the associated effective sensing distance can be measured experimentally. The particular distance of the coil 14, 72 from the element or surface being sensed will depend upon the particular application. Generally, a range of mounting distances is possible. For example, the coil 14, 72 could be placed relatively close to the element or surface being sensed provide that the coil 14, 72 is not damaged during OFF conditions. Alternatively, the coil 14, 72 could be placed more than one radius away from the element or surface being sensed in order to reduce mechanical abuse susceptibility, provided that the structure of the door 78 provided for relatively greater movement of the outer skin 90 during non-crash, abuse events. Testing has shown that using a bridge circuit in the signal conditioner/preprocessor circuit 114 to improve sensitivity, changes to signal from coil 14, 72 responsive to the element or surface being sensed can be detected even when the distance from the coil 14, 72 to the element or surface being sensed is greater than one radius, however electromagnetic interference may limit the extent to which this extended range may be utilized in some situations.
Generally the coil 14, 72 comprises an element or device that operates in accordance with Maxwell's and Faraday's Laws to generate a first magnetic field 94 responsive to the curl of an associated electric current therein, and similarly to respond to a time-varying first magnetic field 94 coupled therewith so as to generate a voltage or back-EMF thereacross responsive thereto, responsive to the reluctance of the magnetic circuit associated therewith.
The conductive elements 86, 88 each comprise, for example, a thin metal sheet, film or coating, comprising either a paramagnetic or diamagnetic material that is relatively highly conductive, e.g. aluminum or copper, and which, for example, could be an integral part of the second portion 82 of the door 78. For example, the conductive elements 86, 88 could be in the form of relatively thin plates, a film, a tape (e.g. aluminum or copper), or a coating that is mounted on, applied to, or integrated with existing or supplemental structures associated with the door beam 92 and the inside surface of the outer skin 90 of the door 78 respectively.
The frequency of the oscillator 98 is adapted so that the corresponding oscillating magnetic field generated by the at least one coil 14, 72 both provides for generating the associated eddy currents 102 in the conductive elements 86, 88, and is magnetically conducted through the ferromagnetic elements of the door 78 and proximate structure of the vehicle 12.
The at least one coil 14, 72 is responsive to both the first magnetic field 94 generated by the at least one coil 14, 72 and a second magnetic field 104 generated by the eddy currents 102 in the conductive elements 86, 88 responsive to the first magnetic field 94. The self-impedance of the coil 14, 72 is responsive to the characteristics of the associated magnetic circuit, e.g. the reluctance thereof and the affects of eddy currents in associated proximal conductive elements. Accordingly, the coil 14, 72 acts as a combination of a passive inductive element, a transmitter and a receiver. The passive inductive element exhibits self-inductance and self resistance, wherein the self-inductance is responsive to the geometry (coil shape, number of conductors, conductor size and cross-sectional shape, and number of turns) of the coil 14, 72 and the permeability of the associated magnetic circuit to which the associated magnetic flux is coupled; and the self-resistance of the coil is responsive to the resistivity, length and cross-sectional area of the conductors constituting the coil 14, 72. Acting as a transmitter, the coil 14, 72 generates and transmits a first magnetic field 94 to its surroundings, and acting as a receiver, the coil 14, 72 generates a voltage responsive to a time varying second magnetic field 104 generated by eddy currents in associated conductive elements within the surroundings, wherein the eddy currents are generated responsive to the time varying first magnetic field 94 generated and transmitted by the coil 14, 72 acting as a transmitter. The signal generated by the coil 14, 72 responsive to the second magnetic field 104 received by the coil 14, 72, in combination with the inherent self-impedance of the coil 14, 72, causes a complex current within or voltage across the coil 14, 72 responsive to an applied time varying voltage across or current through the coil 14, 72, and the ratio of the voltage across to the current through the coil 14, 72 provides an effective self-impedance of the coil 14, 72, changes of which are responsive to changes in the associated magnetic circuit, for example, resulting from the intrusion or deformation of proximal magnetic-field-influencing—e.g. metal—elements.
The at least one coil 14, 72 is operatively coupled to a signal conditioner/preprocessor circuit 114, which, for example, provides for preamplification, filtering, synchronous demodulation, and analog to digital conversion of the associated signal(s) therefrom, e.g. as described in U.S. Pat. Nos. 6,587,048 and 6,777,927, which is incorporated herein by reference. The signal conditioner/preprocessor circuit 114 is operatively coupled to a processor 116 which processes the signal therefrom, thereby providing for discriminating a crash, and controlling an associated safety restraint actuator 110—e.g. a side air bag inflator—operatively coupled thereto. More particularly, the signal conditioner/preprocessor circuit 114 provides for determining a measure responsive to the self-impedance of the at least one coil 14, 72 responsive to an analysis of the complex magnitude of the signal from the at least one coil 14, 72, for example, in relation to the signal applied thereto by the associated oscillator 98. For example, in one embodiment, the signal conditioner/preprocessor circuit 114, coil driver 96, oscillator 98 and processor 108 are incorporated in an electronic control unit 120 that is connected to the at least one coil 14, 72 with standard safety product cabling 122, which may include associated connectors.
In operation, the magnetic crash sensor 10.1′″ provides a measure of the relative motion of either the outer skin 90 or the door beam 92 relative to the inner panel 84 of the door 78, for example, as caused by a crushing or bending of the door 78 responsive to a side-impact of the vehicle 12. During non-crash conditions, an oscillating magnetic field resulting from the combination of the first 94 and second 104 magnetic fields would be sensed by the at least one coil 14, 72. If an object impacted the outer skin 90 of the door 78 causing a physical deflection thereof, then this oscillating magnetic field would be perturbed at least in part by changes in the second magnetic field 104 caused by movement or deformation of the associated first conductive element 86 and the associated changes in the associated eddy currents 102 therein. If the impact is of sufficient severity, then the door beam 92 and the associated second conductive element 88 would also be moved or deformed thereby, causing additional and more substantial changes in the associated eddy currents 102 in the second conductive element 88 and the corresponding second magnetic field 104. Generally, the door beam 92 and associated second conductive element 88 would not be perturbed during impacts that are not of sufficient severity to warrant deployment of the associated safety restraint actuator 110, notwithstanding that there may be substantial associated deformation of the outer skin 90 of the door 78. Accordingly, in one embodiment, a magnetic crash sensor 10.1′″ might incorporate the second conductive element 88, and not the first conductive element 86.
Responsive to a crash with an impacting object of sufficient energy to deform the at least one conductive element 80, changes to the shape or position of the at least one conductive element 80 relative to the at least one coil 14, 72 affect the magnetic field affecting the at least one coil 14, 72. A resulting signal is preprocessed by the signal conditioner/preprocessor circuit 114, which provides for measuring the signal across the at least one coil 14, 72 and provides for measuring the signal applied thereto by the associated coil driver 96. The signal conditioner/preprocessor circuit 114—alone, or in combination with another processor 116—provides for decomposing the signal from the at least one coil 14, 72 into real and imaginary components, for example, using the signal applied by the associated coil driver 96 as a phase reference.
Whereas
Referring to
Referring to
Alternatively, the distributed coil 124 may comprise a plurality of coil elements 14, each comprising a winding of a conductor 136, e.g. magnet wire, wound so as to form either a planar or non-planar coil, and bonded to the surface of a substrate 138, wherein the associated coil elements 14 may be either separated from, or overlapping, one another, and the associated windings of a particular coil element 14 may be either overlapping or non-overlapping. The different coil elements 14 may be formed from a single contiguous conductor, or a plurality of conductive elements joined or operative together. The associated distributed coil 124 may comprise multiple layers either spanning across different sides of the substrate 138 or on a same side of the substrate 138. If the conductor 136 so formed were insulated, e.g. as would be magnet wire, then the substrate 138 could comprise substantially any material that would provide for the associated generation of the associated magnetic field 140 by the plurality of coil elements 14. Furthermore, the substrate 138 could comprise either a rigid material, e.g. a thermoset plastic material, e.g. a glass-epoxy composite material or a phenolic material; or a flexible material, e.g. a plastic or composite membrane.
The distributed coil 124 in accordance with any of the above-described embodiments may be encapsulated so as to provide for improved reliability and reduced susceptibility to environmental affects. Furthermore, the distributed coil 124 may be combined with some or all of the associated circuitry, e.g. the oscillator 98 and associated signal conditioner/preprocessor circuit 114, or components thereof, in an associated magnetic sensor module, some or all of which may be encapsulated so as to provide for improved reliability and reduced susceptibility to environmental affects. Alternatively, the distributed coil 124 and associated signal conditioner/preprocessor circuit 114 may be packaged separately.
Referring to
Referring to
A conductive element 18, 80 could also be added to a ferrous element 148, although in order for the affect of the magnetic field component(s) 140 to dominate an affect of a magnetic field within the ferrous element 148, the associated conductive element 18, 80 would need to be thick enough or conductive enough to prevent the original transmitted magnetic field component(s) 140 from penetrating though to the ferrous element 148 on the other side of the conductive element 18, 80, whereby eddy currents 34, 102 in the conductive element 18, 80 would completely cancel the magnetic field at some depth of penetration into the conductive element 18, 80. For example, for a superconducting conductive element 18, 80, there would be no penetration of the magnetic field component(s) 140 into the conductive element 18, 80. Although the depth of penetration of the first magnetic field 26, 94 increases as the conductivity of the conductive element 18, 80 decreases, an aluminum or copper conductive element 18, 80 would not need to be very thick (e.g. 2.5 mm or less) in order to substantially achieve this affect. The depth of penetration of magnetic fields into conductive elements 18, 80 is known from the art using eddy currents for non-destructive testing, for example, as described in the technical paper eddyc.pdf available from the internet at http://joe.buckley.net/papers, which technical paper is incorporated herein by reference. Generally, if the thickness of the conductive element 18, 80 exceeds about three (3) standard depths of penetration at the magnetic field frequency, then substantially no magnetic field will transmit therethrough. Responsive to a crash with an impacting object of sufficient energy to deform or translate the conductive element 18, 80, changes to the shape or position thereof relative to at least one of the coil elements L1′, L2′, L3′ affects at least one of the associated magnetic field components 140.1, 140.2 and 140.3, which affect is detected by an associated signal conditioner/preprocessor circuit 114 operatively coupled to the coil elements L1′, L2′, L3′ as described hereinabove.
The conductive element 18, 80 may comprise a pattern 150 adapted to control associated eddy currents 34, 102 therein. For example, the conductive element 18, 80 may be adapted by either etching, forming (e.g. which a sheet metal forming tool), coating (e.g. with an E-coat process), or machining the pattern 150 in or on a surface thereof so as to control, e.g. limit, the associated eddy currents 34, 102. The format, depth, and distribution of the pattern 150 can be optimized to provide optimal sensing resolution for a given operating frequency. The conductive element 18, 80 could be designed so that the movement or deformation thereof is highly visible to at least one of the plurality of coil elements 14 so as to increase the confidence of a timely associated crash or proximity detection. Each portion of the pattern 150 extends through at least a portion of the conductive element 18, 80 so as to provide for blocking or impeding eddy currents 34, 102 thereacross, so that the associated eddy currents 34, 102 become primarily confined to the contiguous conductive portions 152 therebetween or thereunder. For example, the pattern 150 may adapted to a frequency of the associated at least one time-varying signal.
Referring to
A conductive element 158 may be adapted to cooperate with at least one of the plurality of coil elements 14 so as to provide for shaping, controlling or limiting at least one the associated magnetic field components 140. For example, referring to
As another example, referring to
Referring to
The at least one first coil 14 is operatively coupled to a corresponding coil driver 28, 56, 96, which is in turn operatively coupled to an oscillator 30, 58, 98, wherein an oscillatory signal from the oscillator 30, 58, 98 is applied by the coil driver 28, 56, 96 so as to cause an associated current in the first coil 14, responsive to which the first coil 14 generates a magnetic field 26, 140 comprising magnetic flux 186 in associated first 188.1 and second 188.2 magnetic circuits. The oscillator 30, 58, 98 generates a oscillating signal, for example, having either a sinusoidal, square wave, triangular or other waveform shape, of a single frequency, or a plurality of frequencies that are either stepped, continuously swept or simultaneous. The frequency is adapted so that the resulting magnetic field 26, 140 is conducted through the first 188.1 and second 188.2 magnetic circuits. For example, the oscillation frequency would typically be less than about 50 KHz for a steel structure, e.g. 10 to 20 KHz in one embodiment. The magnetic field 26, 140 is responsive to the reluctance of the associated first 188.1 and second 188.2 magnetic circuits, which is affected by a crash involving the elements thereof and/or the gaps 178 therein. The magnetic flux 186 propagates within the associated magnetically permeable material of the first 188.1 and second 188.2 magnetic circuits. The doors 78.1, 78.2 are isolated from the remainder of the vehicle 12, e.g. the frame, by the gaps 178 therebetween, except where the hinges 176 and door latch assemblies 172.1, 172.2 provide relatively lower reluctance paths therebetween.
The at least one first coil 14 can each be used alone in a single-port mode to both generate the magnetic flux 186 and to detect a signal responsive thereto, and may also be used in cooperation with one or more magnetic sensors 190 in a multi-port mode. For example, one or more first coils 14 at corresponding first locations 166 can be used in cooperation with a plurality of magnetic sensors 190.1, 190.2 at a corresponding plurality of second locations 192.1, 192.2 of the vehicle 12. For example, for a first coil 14 located around the striker 170.1 of the door latch assembly 172.1 of the front door 78.1, in one embodiment, the magnetic sensors 190.1, 190.2 comprise a second coil 194 around a hinge 176 of the front door 78.1, and a third coil 196 around a striker 170.2 of the door latch assembly 172.2 of the rear door 78.2 and the striker 170.2 of the door latch assembly 172.2 of the rear door 78.2 is operatively coupled to the C-pillar 175 of the vehicle 12. The second 194 and third 196 coils surround metallic elements of the associated first 188.1 and second 188.2 magnetic circuits, and the magnetic flux 186 propagating within the associated magnetically permeable material of the first 188.1 and second 188.2 magnetic circuits also flows through the second 194 and third 196 coils surrounding the associated magnetically permeable material. The second 194 and third 196 coils generate voltage signals responsive to the oscillating magnetic flux 186, or component thereof, directed along the axis of the second 194 and third 196 coils respectively, in accordance with Faraday's law of magnetic induction.
In operation in accordance with a single-port mode, a time varying signal 198 is generated by a signal source 200, for example, and oscillator or a pulse generator, and applied to the at least one first coil 14 by an associated coil driver 202. For example, an oscillatory signal source 200 would function similar to that described hereinabove for any of oscillators 30, 58 and 98, and the coil driver 202 would function similar to that described hereinabove for any of coil drivers 28, 56 and 96, depending upon the particular application. The two leads of the at least one first coil 14 define a port Ai, which is also connected to an associated signal conditioner/preprocessor circuit 114 which processes a signal associated with the at least one first coil 14, the signal being responsive to the time varying signal 198 applied thereto, and responsive to the self-impedance of the associated at least one first coil 14. As disclosed more fully hereinbelow, the coil driver 202 can be incorporated into the circuitry of the associated signal conditioner/preprocessor circuit 114. The at least one first coil 14 generates a magnetic field 26, 140 in and throughout the associated magnetic circuit 188.1, 188.2, responsive to the time varying signal 198 applied thereto. For example, for an at least one first coil 14 located within a gap 178 between a fixed body structure and a proximal surface of another element of the body provides for detecting a relative movement between the fixed body structure and the proximal surface, responsive to a crash, for example, responsive to an intrusion of the proximal surface relative to the fixed body structure.
In a two-port mode, one or more associated magnetic sensors 190, 190.1, 190.2 at respective second locations 192.1, 192.2 are operatively coupled at a port Bj to a corresponding one or more signal conditioner/preprocessor circuits 40, which provide for generating a signal responsive to the magnetic field 26, 140 at the corresponding one or more second locations 192.1, 192.2.
The signal conditioner/preprocessor circuit(s) 114, 40 are operatively coupled to an associated processor 204, and provide for conditioning the associated signal(s) from the at least one first coil 14 and one or more associated magnetic sensors 190, 190.1, 190.2. The signal conditioner/preprocessor circuit(s) 114, 40 demodulate the signal(s) from the associated at least one first coil 14 or one or more associated magnetic sensors 190, 190.1, 190.2 with an associated demodulator, and converts from analog to digital form with an associated analog-to-digital converter which is sampled and input to the processor 204. The signal conditioner/preprocessor circuit(s) 114, 40 may also provide for amplification. Changes to the magnetic field 26, 140 at a particular location in the first 188.1 and second 188.2 magnetic circuits propagate therewithin at the speed of light and are seen therethroughout. Accordingly, the magnetic field 26, 140 sensed by the at least one first coil 14, and possibly by one or more associated magnetic sensors 190.1, 190.2, contains information about the nature of the remainder of the magnetic circuit, including the front 78.1 and rear 78.2 doors and the adjacent A-pillar 184, B-pillar 174 and C-pillar 175, any of which could be involved in, or affected by, a crash, responsive to which the processor 204 provides for detecting the crash and controlling a safety restraint actuator 44 responsive thereto. In
Referring to
For example, in a ninth embodiment of a coil 14.9, the axis 210 of the gap coil 206 is substantially perpendicular to the edge 182 of the A-pillar 184 and to the front edge 180 of the front door 78.1 when the front door 78.1 is closed. The coil 14.9 is attached to the A-pillar 184 with a fastener 212 through the associated spool 208, e.g. a socket head screw 212.1 through a counterbore in the spool 208. The magnetic permeability of the fastener 212 can be adapted in accordance with the sensing or field generating requirements of the associated gap coil 206. For example, the fastener 212 associated with the coil 14.9 is substantially aligned with the axis 210 of the gap coil 206, so that a fastener 212 of a material with a relatively high permeability, e.g. carbon steel or electrical steel, will tend to concentrate the magnetic flux 186 through the gap coil 206, whereas a fastener 212 of a material with a relatively low permeability, e.g. stainless steel, aluminum or brass, will tend to emulate an air core so that the coil 14.9 has less of a tendency to perturb the associated first 188.1 or second 188.2 magnetic circuit. As another example, in a tenth embodiment of a coil 14.10, the axis 210 of the gap coil 206 is substantially parallel to the edge 182 of the A-pillar 184 and to the front edge 180 of the front door 78.1, so as to be substantially aligned with the length of the associated gap 178. The coil 14.10 is shown attached to the A-pillar 184 with a fastener 212 through a flange that depends from the associated spool 208.
Referring to
Referring to
Referring to
The gap coil assemblies 218 illustrated in
Referring to
Referring to
The signal from the signal conditioner/preprocessor circuit 114 responsive to the at least one coil 14 may be used to detect changes to the associated magnetic circuit 188 to which the at least one coil 14 is operatively associated. Generally, the changes to the associated magnetic circuit 188 comprise a combination of effects, including 1) changes to the reluctance of the magnetic circuit 188 to which the at least one coil 14 is magnetically coupled, and 2) eddy currents 34, 102 induced in a proximal conductive element 88 responsive to a first magnetic field 26, 94 generated by the at least one coil 14, which generate a first magnetic field 26, 94 in opposition to the first magnetic field 26, 94, thereby affecting the self-induced voltage in the at least one coil 14.
Referring to
Referring to
The signal conditioner/preprocessor circuit 114 provides for detecting the impedance Z of at least one coil element 14, or of a combination or combinations of a plurality of coil elements 14. For example, referring to
The coil element L′, or a combination of the coil elements L′, is/are magnetically coupled, either directly or indirectly, to at least a portion of the vehicle 12 susceptible to deformation responsive to a crash, wherein changes thereto (e.g. deformation thereof) responsive to a crash affects the reluctance of the associated magnetic circuit 68, 188, and/or induces eddy currents 34, 102 in an associated proximal conductive element 18, either of which affects the current i in the coil element L′, or a combination of the coil elements L′, detection of which provides for detecting the resulting associated change in the magnetic condition of the vehicle 12 associated with the deformation of the associated portion of the vehicle 12 responsive to the crash.
Referring to
C1+C2·x (1)
which includes a bias component C1 and a displacement component C2·x responsive to static displacement x of the conductive element 80 relative to the coil 14; and a second signal component 254 given by:
which is responsive to the velocity of the conductive element 80 relative to the coil 14, wherein the phasor phase values of the first 252 and second 254 signal components are referenced with respect to the drive current signal Idr applied by the time-varying current source 250 and are orthogonal with respect to one another in the complex plane. It is hypothesized that the velocity dependent second signal component 254 is related to the momentum transferred to the vehicle 12 by the object or other vehicle in collision therewith, and that the displacement component C2·x is related to the energy absorbed by the vehicle 12 during the crash, wherein relatively soft vehicles 12 would tend to absorb relatively more energy and would tend to produce relatively more low frequency signals, and relatively stiff vehicles 12 would tend to receive relatively more momentum and would tend to produce relatively more high frequency signals. Furthermore, the real component 256 of the complex voltage signal V is related to the resistive losses in the coil 14 or the eddy current losses in the conductive element 80, whereas the imaginary component 258 is related to the self-inductance of the coil 14 which is responsive to the permeability of the magnetic elements inductively coupled therewith.
Referring to
The first 266 and second 270 sense terminals of the coil driver 28, 56, 96 are of relatively high impedance, so that the first RS1 and second RS2 sense resistors and the coil 14 each carry substantially the same current I from the coil driver 28, 56, 96. The voltage Vout at the output 284 of summing and difference amplifier 276 is given as:
Vout=(V1−V4)−(V2−V3)=I·(RS1+RS2) (3)
which is equal to the total voltage drop across the sense resistors RS1, RS2, which provides a measure of the current through the coil 14. Accordingly, given that the voltage VL across the coil 14 is controlled to a value of twice the peak-to-peak AC voltage VAC of the oscillator 30, 58, 98, and is therefore known, the measure of current I through the coil 14—responsive to Vout—can be used in combination with the known voltage VL across the coil 14, to determine the self-impedance Z of the coil 14. Alternatively, the current I through the coil 14 can be demodulated into in-phase I and quadrature-phase Q components phase-relative to the sinusoidal time varying signal 198 of the oscillator 30, 58, 98 so as to provide substantially equivalent information, wherein the in-phase component I provides a measure of the effective resistance R of the coil 14, and the quadrature-phase component Q provides a measure of the effective impedance Z of the coil 14. In accordance with this latter approach, the output 284 of the summing and difference amplifier 276 is filtered by a low-pass filter 286, converted from analog to digital form by an analog-to-digital converter 288, and demodulated into the in-phase I and quadrature-phase Q components by a demodulator 290 which is phase-referenced to the time varying signal 198 of the oscillator 30, 58, 98.
The in-phase I and/or quadrature-phase Q component, individually or in combination, is/are then processed by a crash sensing algorithm 292 in the processor 108, 204 to provide for discriminating or detecting crash events that are sufficiently severe to warrant the deployment of the safety restraint actuator 44. For example, in one set of embodiments, the in-phase component I, possibly in combination with the quadrature-phase Q component, is processed to provide for discriminating or detecting crash events that are sufficiently severe to warrant the deployment of the safety restraint actuator 44. Alternatively, the in-phase component I, possibly in combination with the quadrature-phase Q component, may be used to provide a safing signal to prevent the actuation of a safety restraint actuator 44 absent a crash of sufficient severity to warrant a possible deployment thereof.
Referring to
Referring to
Referring to
Referring to
For ideal first 302 and second 304 operational amplifiers, and for:
the voltage VL across the coil 14, L′ is given by:
VL=V2−V3=α·(VB−VA)=2·α·A·sin(ωt) (8)
Accordingly, the feedback control loop provides for controlling the value of the voltage VL across the coil 14, L′, and, for example, setting this to a value higher than would be obtained, for example, with the third embodiment of the signal conditioning circuit 294.3 illustrated in
Referring to
Vout=(V1−V4)−(V2−V3)=(RS1+RS2)·iL (12)
The remaining portions of the signal conditioning circuit 294.5 function the same as for the fourth embodiment of the signal conditioning circuit 294.4 illustrated in
V1=V2−V3=α·(VB−VA)+(1+α)·((VCM1−VCM2)+(δ1−δ2)) (13)
Under the conditions of Equation (6), this reduces to:
VL=V2−V3=α·(VB−VA)+(1+α)·(δ1−δ2) (14)
Under the conditions of Equations (7) and (8), this reduces to:
VL=V2−V3=2·α·A·sin(ωt)+(1+α)·(δ1−δ2) (15)
The AC component of the voltage VL across the coil 14, L′ has a value of:
VLAC=(V2−V3)AC=2·α·A·sin(ωt), (16)
which, for α=1, is comparable to that of third embodiment of the signal conditioning circuit 294.3 illustrated in
Accordingly, the DC bias voltage sources δ1 and δ2 cause the voltage VL across the coil 14, L′ to have a DC bias of:
(1+α)·(δ1−δ2), (17)
which, for α=1 and δ=max(|δ1|,|δ2|), can have a value as great as 4δ—because the DC bias voltage sources δ1 and δ2 are uncorrelated—which causes a corresponding DC bias current in the coil 14, L′, which might adversely magnetize the vehicle 12.
Referring to
Letting:
the second common mode voltage signal VCM2 is then given by:
VCM2VCM1+G·(V2−V3)+(1+G)·δ5, (17)
and the resulting voltage VL across the coil 14, L′ is then given by:
wherein a prospective DC offset of the fifth operational amplifier 310 is represented by a DC bias voltage source δ5 at the non-inverting input thereof.
For the first VA and second VB complementary output signals given by Equations (7) and (8) respectively, the resulting voltage VL across the coil 14, L′ is given by:
For α=1, the resulting voltage VL across the coil 14, L′ is given by:
Accordingly, as the gain G is increased, the magnitude of the first component of Equation (20)—which includes the entire AC component and the DC components attributable to the DC bias voltage sources δ1 and δ2—decreases. For example, for G=1, the voltage VL across the coil 14, L′ is given by:
VL=A·sin(ωt)+(δ1−δ2)−1.5·δ5, and (21)
and as the gain G approaches infinity, the voltage VL across the coil 14, L′ approaches the value of the DC bias voltage source δ5 associated with the fifth operational amplifier 310:
VL=−δ5. ((22)
Accordingly, with sufficient gain G, the sixth embodiment of the signal conditioning circuit 294.6 illustrated in
Referring to
The seventh embodiment of the signal conditioning circuit 294.7 illustrated in
Referring to
Referring to
The tenth embodiment of the signal conditioning circuit 294.10 further illustrates an example of a circuit 317 for generating the first common mode voltage signal VCM1. For example, the circuit 317 comprises a first voltage divider 318 of resistors R7 and R8 fed by a supply voltage source VS. The output of the voltage divider 318 is buffered by an associated sixth operational amplifier 320 configured as an associated buffer amplifier 320′. For example, for resistors R7 and R8 of equal value, the resulting first common mode voltage signal VCM1 would be half the value of the supply voltage source VS.
The tenth embodiment of the signal conditioning circuit 294.10 further illustrates an example of an embodiment of the associated oscillator 300, wherein the output signal VA is generated by a seventh operational amplifier 322, the non-inverting input of which is coupled to the output of a second voltage divider 324 comprising resistors R9 and R10 fed by the first common mode voltage signal VCM1, the inverting input of which is coupled by an input resistor R11 to an oscillator 30, 58, 98, and by a feedback resistor R12 to the output of the seventh operational amplifier 322. For resistors R9 and R10 of equal value, and for resistors R11 and R12 of equal value, and for the output of the oscillator 30, 58, 98 given by A·sin(ωt), then the output signal VA is given by Equation (7).
Furthermore, the output signal VB is generated by an eighth operational amplifier 326, the non-inverting input of which is coupled to the first common mode voltage signal VCM1 through a first input resistor R13, and to the oscillator 30, 58, 98 through a second input resistor R14; and the non-inverting input of which is coupled by a an input resistor R15 to ground, and by a feedback resistor R16 to the output of the eighth operational amplifier 326. For resistors R13 and R14 of equal value, and for resistors R15 and R16 Of equal value, and for the output of the oscillator 30, 58, 98 given by A·sin(ωt), then the output signal VB is given by Equation (8).
Referring to
As with the embodiments illustrated in
Furthermore, a bias control circuit 344 provides for substantially nulling any DC current bias in the current iL through the coil 14, L′. For example, in accordance with a first aspect of a bias control circuit 344.1, for example, as illustrated in
In accordance with a second aspect of a bias control circuit 344.2, for example, as illustrated in
Yet further, as with the embodiments illustrated in
In accordance with a third aspect of a bias control circuit 344.3, for example, as illustrated in
The voltage Vout providing a measure of the current iL through the coil 14, L′ is filtered with a band-pass filter 350 and then converted to digital form with an associated first analog-to-digital converter 288′. For example, in one embodiment, the band-pass filter 350 is a second order two-input fully differential switched capacitor bandpass filter having a Butterworth approximation, and a programmable center frequency that, responsive to the processor 108, 204, is automatically set to the same frequency as that of the sine shaper 328 and associated clock 330. In this embodiment, the band-pass filter 350 has a fixed 6 kiloHertz passband and is used to limit the susceptibility to out-of-band energy radiated from other sources.
A ninth operational amplifier 352 configured as a differential amplifier provides for measuring the actual voltage across the voltage VL across the coil 14, L′, notwithstanding that this is otherwise controlled by the circuitry associated with the linear driver 342 and bias control circuit 344 as described hereinabove. More particularly, the second node 264 coupled to a first terminal of the coil 14, L′, at a voltage V2, is coupled through a first input resistor R23 to the non-inverting input of the ninth operational amplifier 352, which is also connected to the DC common mode voltage signal VCM ground through a resistor R24. Furthermore, the third node 268 coupled to the second terminal of the coil 14, L′, at a voltage V3, is coupled through a second input resistor R33 to the inverting input of the ninth operational amplifier 352, which is also connected to the output thereof a feedback resistor R34. Accordingly, the output of the ninth operational amplifier 352, designated as voltage VOUT, is given as follows:
VDrive=γ·(V2−V3) (23)
wherein the gain γ is given by:
In various embodiments, for example, the gain γ may be programmable responsive to the processor 108, 204. For example, in one embodiment, the gain γ is programmable over a range of 1 to 80 volts/volt, so that the resulting voltage VDrive from the ninth operational amplifier 352 is within the range of 0-1 volt peak-to-peak for input to an associated second analog-to-digital converter 354.
Referring to
Referring to
In one embodiment, the sigma-delta converter 358 is implemented with a fully differential second-order switched-capacitor architecture, using a sampling rate of 4 megahertz, with a usable differential input range of 0-1 volt peak-to-peak. In one embodiment, the sigma-delta converter 358 is principally used at about one half of full scale in order to avoid distortion from the one-bit digital-to-analog converter 374 which can occur for input signals have a magnitude greater than about eighty percent of full scale. Above full scale, the one-bit digital-to-analog converter 374 would overload, causing a loss of signal integrity. Using only half of full scale to avoid distortion, the sigma-delta converter 358 would have an effective gain of 0.5, although this can be compensated for in the associated decimation filter 362 which, for example, in one embodiment, is adapted to utilize a twelve-bit span for a one volt peak-to-peak input signal.
Referring to
The number of bits needed in the accumulators 384 to avoid overflow errors is defined by:
w=K·log2(N)+b (28)
wherein K is the decimator order (e.g. 3), N is the decimation ratio (e.g. 128), and b is the number of bits entering the decimator (e.g. 1 or 8). For example, for K=3, N=128 and b=1, the accumulators 384 are 22 bits wide, whereas for b=8, the accumulators 384 would be 29 bits wide. Each of the accumulators 384 is defined by the following equation:
Vaccn+1=Vaccn+Vinn (29)
For example, for an input clock rate of 4 megahertz, the output of the last accumulator 384 illustrated in
Vdiffn+1=Vinn+1−Vinn (30)
For example, in one embodiment, the output of the last differentiators 386 of the first 382.1 and second 382.2 decimators is truncated to twelve bits. The mixing process associated with the first and second mixers inherently has a gain of ½ (as a result of an associated ½ cosine factor), and this is compensated in the decimator 382 so that the twelve-bit span of the digital output thereof corresponds to a one volt peak-to-peak signal at the input to the sigma-delta converter 358. The associated generic equation of the decimator 382 is given by:
f=[(1−z−N)/(1−z−1)]K (31)
Referring to
Referring again to
The outputs of the first 376.1 and second 376.2 demodulators are respectively filtered by respective first 398.1 and second 398.2 low-pass filters, and are then respectively filtered by respective first 400.1 and second 400.2 band-pass filters. For example, in one embodiment, the first 398.1 and second 398.2 low-pass filters are second order digital filters with a programmable type (e.g. Butterworth or Chebyshev) and programmable filter coefficients k and gain factors G, the same type and values for each filter 398.1, 398.2; and the first 400.1 and second 400.2 band-pass filters are fourth order digital filters with a programmable type (e.g. Butterworth or Chebyshev) and programmable coefficients, the same type and values for each filter 400.1, 400.2. The gain factors G in each filter are adapted to provide for unity gain through each of the filters 398.1, 398.2, 400.1, 400.2. For example, the filter coefficients k and gain factors G are stored in a twelve-bit register in fixed point two's complement number format.
For example, the first 398.1 and second 398.2 low-pass filters are given generally by the following transfer function:
the first 400.1 and second 400.2 band-pass filters are given generally by the following transfer function:
In one embodiment, the outputs of the first 400.1 and second 400.2 band-pass filters are averaged using a four point averaging process, for example, using a running average implemented with a moving window, so as to provide resulting in-phase (I) and quadrature (Q) phase components of the voltage Vout representative of the current iL through the coil 14, L′ at an update rate of about 7.8 kilohertz. In the present embodiment, the low-pass filters 398.1, 398.2 would not be used below 300 Hertz because of stability problems due to quantization errors in the associated gain factors G and filter coefficients k. The resulting in-phase I and quadrature-phase Q data can be used to calculate, with twelve-bit accuracy, the magnitude of the and phase of the current iL through the coil 14, L′, as follows:
wherein the phase is quadrant-corrected so that the resulting phase value is between −180° and +180°, with 0° on the positive I axis, 90° on the positive Q axis.
The output of a second sigma-delta converter 358.2 associated with the second sigma-delta analog-to-digital converter 356.2 is filtered with a second low-pass sync filter 360.2 and then decimated with a second decimation filter 362.2, so as to generate the digital representation—in one embodiment, for example, a twelve-bit representation—of the voltage VDrive, representative of the voltage VL across the coil 14, L′. For example, in one embodiment the second low-pass sync filter 360.2 and the second decimation filter 362.2 are embodied in a second decimator 382.2, similar to the first decimator 382.1 described hereinabove, except that the output thereof is a ten-bit digital word. The output of the second decimator 382.2 is operatively coupled to a second demodulator 376.2 which demodulates an over-sampled signal (e.g. at 4 megahertz) from the second sigma-delta converter 358.2 into an in-phase component (I) of the voltage VDrive across the coil 14, L′. The second demodulator 376.2 uses the digital time series 332 from the sine shaper 328 to demodulate the in-phase (I) component of the voltage VDrive down to a corresponding DC level, albeit the pulse density modulated (PDM) equivalent thereof, wherein, for example, in one embodiment, the digital time series 332 from the sine shaper 328 is fed into an associated third mixer 376.3′ of the third demodulator 376.3 as an N-bit stream at the same over-sampled clock rate (e.g. 4 megahertz) as the signal from the second sigma-delta converter 358.2. The demodulated output from the third mixer 376.3′ is then filtered by a third low-pass filter 398.3, which is similar to the first 398.1 and second 398.2 low-pass filters described hereinabove.
The various signal conditioning circuits 294 in accordance with a first aspect illustrated in
Referring to
In accordance with a first feature, first 402.1 and second 402.2 LC filters are respectively placed in parallel with the first RS1 and second RS2 sense resistors, respectively, wherein the first LC filter 402.1 comprises a first inductor L1 in parallel with a first capacitor C1, and the second LC filter 402.2 comprises a second inductor L2 in parallel with a second capacitor C2, wherein, for example, the resonant frequencies of the first 402.1 and second 402.2 LC filters would be substantially equal to the operating frequency of the associated oscillator 98. Accordingly, at the normal operating frequency of the signal conditioning circuit 294, the impedances of the first 402.1 and second 402.2 LC filters would be relatively high so as to not substantially perturb the operation of the associated signal conditioning circuit 294, whereas at frequencies substantially different from the normal operating frequency of the signal conditioning circuit 294, the impedances of the first 402.1 and second 402.2 LC filters would be relatively low so as to substantially attenuate any associated voltages across the first RS1 and second RS2 sense resistors, thereby substantially attenuating a resulting associated voltage Vout from the summing and difference amplifier 276 representative of the current iL through the coil 14, L′. Accordingly, the first 402.1 and second 402.2 LC filters provide for substantially attenuating the affects of electromagnetic interference (EMI) on the output of the signal conditioning circuit 294 at frequencies that are substantially different from the normal operating frequency thereof.
Referring to
Alternatively, the signal conditioning circuit 294 can be operated at a plurality of different frequencies, i.e. by operating the associated oscillator 30, 58, 98 at a plurality of different frequencies, for example, which are either sequentially generated, fore example, stepped or chirped, or simultaneously generated and mixed, wherein for at least three different frequency components, the associated processor 108, 204 can be adapted to provide for generating a corresponding associated spectrally dependent detected values, wherein an associated voting system can then be used to reject spectral component values that are substantially different from a majority of other spectral component values, for example, as a result of an electromagnetic interference (EMI) at the corresponding operating spectral frequency component(s) of the oscillator 30, 58, 98 of the spectral component that becomes rejected.
Referring again to
In accordance with a third feature, the sum-and-difference amplifier circuit 346 is adapted to provide for injecting a self-test signal VT from a balanced signal source 414 therein so as to test the operation thereof, wherein the balanced signal source 414, controlled by associated switch elements 416, e.g. electronic switches, e.g. controlled by software, is injected through respective first RT1 and second RT2 resistors to the to non-inverting 280 and inverting 282 inputs, respectively, of the associated operational amplifier 278 of the sum-and-difference amplifier circuit 346, wherein, responsive to the injection of the predetermined self-test signal VT through the associated switch element 416, if the resulting change in the voltage Vout from the sum-and-difference amplifier circuit 346 differs from a predetermined amount by more than a threshold, then an error signal would be generated indicative of a malfunction of the associated sum-and-difference amplifier circuit 346.
Referring to
Referring to
Referring to
Referring to
Examples of various notch filter 442 circuit embodiments are illustrated in
Referring to
and the lower corner frequency f1 at a 20 dB gain reduction is given by:
Various other embodiments of notch filters 442 are known in the art, for example, as described by Adel S. Sedra and Kenneth C. Smith in Microelectronic Circuits, Third Edition, Oxford University Press, 1991, Section 11.6, pages 792-799 which is incorporated herein by reference. For example, referring to
Referring to
For example, referring to
Referring to
Accordingly, for the fifteenth embodiment of the signal conditioning circuit 294.15 illustrated in
Referring to
Referring to
Referring to
It should be understood that any of the above embodiments incorporating a pair of sense resistors RS may be adapted so that the associated current measure 348 that provides a measure of the current iL through the coil 14, L′ is responsive only to the voltage across one of the two sense resistors RS, rather than to both, for example, by replacing the summing and difference amplifier 276 with a difference amplifier that generates a signal responsive to the voltage drop across one of the two sense resistors RS, or across a single sense resistors RS of the associated series circuit 242.
Furthermore, referring to
VA=VCM1−VAC (39)
which will be monopolar if the magnitude of the sinusoidal voltage VAC is less than or equal to the magnitude of the DC common mode voltage signal Vcm1.
The output VA of the monopolar signal generator 600 is operatively coupled through a third resistor R3 to the inverting input of a second operational amplifier 606, which is used as a driver 606′ to drive a series circuit 608 comprising the sense resistor RS between a first node 260 and a second node 264, in series with the coil 14, L′ between the second node 264 and a third node 268, i.e. so as to apply a voltage across the series circuit 608 which causes a current iL therethrough. More particularly, the output of the second operational amplifier 606 is operatively coupled to a first terminal of the sense resistor RS at the first node 260 of the series circuit 608, and the second terminal of the sense resistor RS at the second node 264 of the series circuit 608 is operatively coupled to a buffer amplifier 610′ comprising a third operational amplifier 610, the output of which is operatively coupled through a fourth resistor R4 to the inverting input of the second operational amplifier 606. The non-inverting input of the second operational amplifier 606 is operatively coupled to the DC common mode voltage signal VCM1. Accordingly, the buffer amplifier 610′ applies the voltage V2—of the second node 264 of the series circuit 608—to the fourth resistor R4 which feeds back to the inverting input of the second operational amplifier 606, and which, for equal values of the third R3 and fourth R4 resistors, controls the voltage V2 at the second node 264 of the series circuit 608 as follows:
V2=VCM1+VAC (40)
The DC common mode voltage signal Vcm1 is applied as voltage V3 to the terminal of the coil 14, L′ at the third node 268 of the series circuit 608. Accordingly, the voltage VL across the coil 14, L′, which is between the second 264 and third 268 nodes of the series circuit 608, is then given by:
VL=V2−V3=(VCM1+VAC)−VCM1=VAC (41)
Accordingly, the driver 606′ configured with feedback through the buffer amplifier 610′ from the second node 264 of the series circuit 608 provides for controlling the voltage VL across the coil 14, L′.
The first 260 and second 264 nodes of the series circuit 608—i.e. across the sense resistor RS—are then operatively coupled to the inputs of a first differential amplifier 612, the output voltage VOUT of which is responsive to the voltage drop VRS across the sense resistor RS, which provides a measure of current through the coil 14, L′, and which is also biased by the DC common mode voltage signal VCM1 so as to provide for single-supply operation thereof.
Equation (41) shows that under ideal conditions, the voltage VL across the coil 14, L′ does not exhibit a DC bias, so that under these conditions, there would be no corresponding DC current component through the coil 14, L′. However, as described hereinabove, a real operational amplifier can exhibit a DC bias, i.e. a non-zero output signal for no input signal, which can in turn cause a corresponding DC bias current in the series circuit 608 and coil 14, L′, which if not otherwise compensated, could possibly be problematic depending upon the magnitude thereof. Accordingly, the embodiments the signal conditioning circuits 294.19-294.23 of
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
Referring to
and the current iL would be given as follows:
If the duration of the pulse 514 were sufficiently long, e.g. t>>, the current iL would approach a value of:
The pulse 514 is held on for a duration sufficient to provide for measuring the time constant τON, for example, responsive to any of the following: 1) the current iL at and associated time t as the current iL is rising, e.g. at the end of a pulse 514 having a duration less than several time constants τON; 2) the rate of change of current iL as the current iL is rising; 3) the time or times required after initiation of a pulse 514 for the current iL to reach a predetermined value or to reach a set of predetermined values; or 4) an integral of the current iL over at least a portion of the period when the pulse 514 is on.
For example, from Equation (43) may be rewritten as:
where τ=τON. The first derivative of the current iL with respect to time is given by:
From Equations (45) and (46), the current iL can be given as a function of the first derivative of the current iL as:
If the current iL is measured as is and i2 at two corresponding different times t1 and t2, and if the first derivative of the current iL is determined as i1′ and i2′ at these same times, then the time constant τON is given by:
From Equations (47) and (44), the effective resistance RL of the coil 14, L′ is then given by:
and the inductance L of the coil 14, L′ is given by:
L=τON·(Rsense+RL) (50)
After the pulse 514 is turned off, e.g. upon the opening of the controlled switch 508 or the FET transistor switch 508′, the energy stored in the coil 14, L′ is dissipated relatively quickly through the parallel circuit path of the second resistor R2 in series with the diode D, having a time constant τOFF given by:
wherein the value of the second resistor R2 is chosen to magnetically discharge the coil 14, L′ to zero current iL before the next pulse 514. A monopolar pulse train 510 as illustrated in
Referring to
Referring to
Referring to
Referring to
LG=R′L·RG·CG (52)
In one embodiment, for example, the resistance RG of second gyrator resistor RG is controlled to control the effective inductance LG of the gyrator 562 so as to balance or nearly balance the four-arm bridge circuit 556, i.e. so that the differential voltage Vout is nulled or nearly nulled. The second capacitor C2 is provided to balance the first capacitor C1, wherein, for example, in one embodiment, the value of the second capacitor C2 is set equal to or slightly greater than the value of the first capacitor C1, but would not be required if the associated capacitances of the cabling and coil 14, L′ were negligible. The resistance of the first gyrator resistor RL′ is provided to balance the combination of the inherent resistance of the coil 14, L′, the resistance of the associated cabling, and the effective resistance of proximal eddy currents upon the coil 14, L′. One or both of the first RL′ and second RG gyrator resistors can be made controllable, e.g. digitally controllable, and the value of the gyrator capacitor CG would be chosen so as to provide for a necessary range of control of the inductance LG of the gyrator 562 to match that of the coil 14, L′, given the associated control ranges of the first RL′ and second RG gyrator resistors. For example, the values of the first RL′ and second RG gyrator resistors can be slowly updated by an associated processor 108, 204 so as to maintain a desired level of balance of the four-arm bridge circuit 556 during normal, non-crash operating conditions. When the four-arm bridge circuit 556 is nulled, i.e. so as to null the differential voltage Vout, then the values of the resistance RL and inductance L of the coil 14, L′ are given as follows:
In another embodiment, the inductance LG of the gyrator 562 is adapted to be slightly lower than the inductance of the coil 14, L′ so that the differential voltage Vout is not completely nulled, so as to provide a continuous small signal during normal operation, which allows for real-time diagnostics of the coil 14, L′ and associated signals and circuitry. Under off-null conditions, the output of the differential amplifier 574 would generally be complex or phasor valued, which would be demodulated, for example into in-phase (I) and quadrature-phase (Q) components,—for example, using circuitry and processes described hereinabove for FIGS. 46-50,—for subsequent processing and/or associated crash detection.
The third aspect of a signal conditioning circuit 554 can be adapted to provide relatively high accuracy measurements, with relatively high resolution, of the self-impedance ZL of a coil 14, L′.
In either mode of operation, i.e. nulled or off-null, and generally for any of the aspects of the signal conditioning circuits described herein, the associated signal detection process may be implemented by simply comparing the output of the signal conditioning circuit with an associated reference value or reference values, wherein the detection of a particular change in a magnetic condition affecting the coil 14 is then responsive to the change in the associated signal or signals relative to the associated value or reference values. Accordingly, whereas the in-phase (I) and quadrature (Q) phase components of the signal can be determined analytically and related to the associated impedance Z of the coil 14, this is not necessarily necessary for purposes of detecting a change in an associated magnetic condition affecting the coil 14, which instead can be related directly to changes in the associated signals from the signal conditioning circuit.
Referring to
ZL=RL+2πf·L (55)
wherein RL and L are the effective resistance and the self-inductance of the coil 14, L′, respectively. Accordingly, for a frequency-dependent applied voltage signal v(f) from the summing amplifier 598, the complex voltage Vsense across the sense resistor Rsense is given by:
wherein the cut-off frequency f0 of the associated low-pass filter comprising the coil 14, L′ in series with the sense resistor Rsense is given by:
The frequency-dependent current iL through the coil 14, L′ is then given by:
having a corresponding frequency dependent magnitude ∥iL∥ and phase φ respectively given by:
The voltage VL across the coil 14, L′ is given by:
VL=v(f)−VSense (61)
which provides a phase reference and therefore has a phase of 0 degrees. The ratio of the voltage VL across the coil 14, L′ to the current iL through the coil 14, L′ provides a measure of the self-impedance ZL of a coil 14, L′. The voltage Vsense is sensed with a differential amplifier 599, the output of which is operatively coupled to a processor 108, 204 for subsequent analysis.
Referring to
Although the signal conditioning circuits 294 described herein have been illustrated for generating a measure responsive to a self-impedance of a coil, in general, these signal conditioning circuits 294 may generally be used to measure the impedance of a two terminal circuit element, or a two terminal combination of circuit elements so as to provide for generating a measure responsive to the self-impedance of the two terminal circuit element or the two terminal a combination of circuit elements.
Referring to
Referring to
Accordingly, the half-sine signal 704 in cooperation with the control of the associated H-switch 706 by the polarity control signal p provides for generating the equivalent of a zero-biased sine waveform across the series circuit 702, the current iL through which is detected by the sum and difference amplifier 718 comprising an operational amplifier 720, the inverting input of which is connected through a first resistor 722 to one terminal of the sense resistor RS, designated by voltage V1, the non-inverting input of which is connected through a second resistor 724 to the other terminal of the sense resistor RS, designated by voltage V2, and through a third resistor 726 to the DC common mode voltage signal VCM1, and the output of which is connected through a fourth resistor 728 to the non-inverting input thereof, and which provides the voltage VOUT representative of the current iL through the coil 14, L′, as follows:
VOUTV2−V1+VCM1=iL·RS+VCM1 (62)
Referring to
Referring to
Referring to
For example, referring to
Referring to
Referring to
Alternatively, referring to
The selection and separation of the frequencies f1, f2 . . . fN is, for example, chosen so as to decrease the likelihood of simultaneous interference therewith by electromagnetic interference (EMI), which can arise from a number of sources and situations, including, but not limited to electric vehicle noise, telecommunications equipment, television receivers and transmitters, engine noise, and lightning. For example, in one embodiment, the frequencies are selected in a range of 25 KHz to 100 KHz. As the number N increases, the system approaches spread-spectrum operation.
It should be understood that frequency diversity may be used with any known magnetic sensor technology, including crash, safing or proximity detection that include but are not limited to systems that place a winding around the undercarriage, door opening or hood of the automobile, place a winding around the front fender of the automobile, placing a ferrite rod inside the hinge coil, or inside the striker coil for magnetic focusing, placing a ferrite rod coil in the gap or space between the doors, or placing a supplemental first coil on the side view rear molding which extends sideward away from the vehicle. This algorithm can also be used with signals that are generated by the magnetic sensor that set up alternate frequencies to create system safing on the rear door to enhance the system safing of the front door, AM, FM or pulsed demodulation of the magnetic signature multitone, multiphase electronics, a magnetically biased phase shift oscillator for low cost pure sine wave generation, a coherent synthetic or phase lock carrier hardware or microprocessor based system, a system of microprocessor gain or offset tuning through D/A then A/D self adjusting self test algorithms, placing a standard in the system safing field for magnetic calibration, inaudible frequencies, and the like.
It should also be understood that the performance of the coil 14, L′ used for either generating or sensing a magnetic field can be enhanced by the incorporation of an associated magnetic core of relatively high magnetic permeability. Furthermore, it should be understood that the particular oscillatory wave form of the oscillators is not limiting and could be for example a sine wave, a square wave, a saw tooth wave, or some other wave form of a single frequency, or a plural frequency that is either stepped or continuously varied or added together and sent for further processing therefrom.
It should be noted that any particular circuitry may be used such as that not limited to analog, digital or optical. Any use of these circuits is not considered to be limiting and can be designed by one of ordinary skilled in the art in accordance with the teachings herein. For example, where used, an oscillator, amplifier, or large scaled modulator, demodulator, and a deconverter can be of any known type for example using transistors, field effect or bipolar, or other discrete components; integrated circuits; operational amplifiers or logic circuits, or custom integrated circuits. Moreover, where used a microprocessor can be any computing device. The circuitry and software for generating, mixing demodulating and processing the sinusoidal signals at multiple frequencies can be similar to that used in other known systems.
Magnetic crash sensors and methods of magnetic crash sensing are known from the following U.S. Pat. Nos. 6,317,048; 6,407,660; 6,433,688; 6,583,616; 6,586,926; 6,587,048; 6,777,927; and 7,113,874; the following U.S. patent application Ser. Nos.: 10/666,165 filed on 19 Sep. 2003; and 10/905,219 filed on 21 Dec. 2004; and U.S. Provisional Application No. 60/595,718 filed on 29 Jul. 2005; all of which are commonly assigned to the Assignee of the instant application, and all of which are incorporated herein by reference.
Referring to
For example, in the combination of the fourth 10.1v and fifth 10.1v embodiments illustrated in
The at least one coil 14, 72 is electrically conductive and is adapted for generating a first magnetic field 94 responsive to a current applied by a coil driver 96, e.g. responsive to a first oscillatory signal generated by an oscillator 98. The magnetic axis 100 of the at least one coil 14, 72 is oriented towards the second portion 82 of the door 78—e.g. towards the inner panel 84 of the door 78, or towards both the inner panel 84 and outer skin 90 of the door 78, e.g. substantially along the lateral axis of the vehicle for the embodiment illustrated in FIGS. 87 and 88—so that the first magnetic field 94 interacts with the conductive elements 80, 86, 88 operatively associated therewith, thereby causing eddy currents 102 to be generated therein in accordance Lenz's Law. Generally the coil 14, 72 comprises an element or device that operates in accordance with Maxwell's and Faraday's Laws to generate a first magnetic field 94 responsive to the curl of an associated electric current therein, and similarly to respond to a time-varying first magnetic field 94 coupled therewith so as to generate a voltage or back-EMF thereacross responsive thereto, responsive to the reluctance of the magnetic circuit associated therewith. For example, the at least one coil 14, 72 may comprise a coil of wire of one or more turns, or at least a substantial portion of a turn, wherein the shape of the coil 14, 72 is not limiting, and may for example be circular, elliptical, rectangular, polygonal, or any production intent shape. For example, the coil 14, 72 may be wound on a bobbin, and, for example, sealed or encapsulated, for example, with a plastic or elastomeric compound adapted to provide for environmental protection and structural integrity. The resulting coil assembly may further include a connector integrally assembled, e.g. molded, therewith. Alternatively, the at least one coil 14, 72 may be formed by wire bonding, wherein the associated plastic coating is applied during the associated coil winding process.
For example, in one embodiment, an assembly comprising the at least one coil 14, 72 is positioned within the door 78 of the vehicle 12 so that the magnetic axis 100 of the at least one coil 14, 72 is substantially perpendicular to the inner panel 84 of the door 78, wherein the inner panel 84 is used as an associated sensing surface. Alternatively, the mounting angle relative to the inner panel 84 may be optimized to account for the shape of the associated metal surface and the relative proximity an influence of an associated door beam 92 or other structural elements relative to the inner panel 84.
In one embodiment, the radius of the coil 14, 72 is adapted to be similar to or greater than the initial distance to the principal or dominant at least one conductive element 80 being sensed thereby. The coil 14, 72 does not require any particular shape, and regardless of the shape, the associated effective sensing distance can be measured experimentally. The particular distance of the coil 14, 72 from the element or surface being sensed will depend upon the particular application. Generally, a range of mounting distances is possible. For example, the mounting distance may be determined by a combination of factors including, but not limited to, the conductivity of the conductive element, the coil size, the range of crash speeds that the coil is designed to sense before being damaged by contact with the conductive element, and the desired time to fire performance for specific crash events.
For example, in one embodiment, a coil 14, 72 of about 10 cm in diameter is located about 40 mm from the inner panel 84 of the door 78, which provides for monitoring about as much as 40 mm of stroke of coil 14, 72 motion, depending upon where along the length of the door beam 92 the coil 14, 72 is mounted and depending upon the door beam 92 intrusion expected during threshold ON (i.e. minimal severity for ON condition) and OFF (i.e. maximal severity for OFF condition) crash events for which the associated safety restraint actuator 44 should preferably be either activated or not activated, respectively. For example, in one embodiment, the location of the coil 14, 72 is adapted so that the associated motion thereof is relatively closely correlated to the bending of the door beam 92. For example, in an alternative mounting arrangement, the coil 14, 72 might be operatively associated with the outer skin 90 of the door 78 if the associated signal therefrom were sufficiently consistent and if acceptable to the car maker. For example, a CAE (Computer Aided Engineering) analysis involving both crash structural dynamics and/or electromagnetic CAE can be utilized to determine or optimized the size, shape, thickness—i.e. geometry—of the coil 14, 72 that both satisfies associated packaging requirements within the door 78 and provides sufficient crash detection capability. The position of the coil 14, 72 may be chosen so that a signal from the coil 14, 72 provides for optimizing responsiveness to a measure of crash intrusion for ON crashes, while also providing for sufficient immunity to OFF crashes, for both regulatory and real world crash modes. For example, the coil 14, 72 operatively associated with the door beam 92 may be adapted to be responsive to the inner panel 84, a conductive element 80, 86 operatively associated therewith, the outer skin 90, or a conductive element 80, 88 operatively associated therewith, either individually or in combination. The bending motion of the door beam 92 relative to the inner panel 84 has been found to be most reliable, however the initial motion of the outer skin 90 can be useful for algorithm entrance and for rapid first estimate of crash speed.
The position, size, thickness of the chosen sensor coil 14, 72 are selected to fit within the mechanical constraints of and within the door 78 associated with electrical or mechanical functions such as window movement, door 78 locks, etc.
For example, referring to
The bracket 900, for example, may be constructed of either a ferromagnetic material, e.g. steel, some other conductive material, e.g. aluminum, or a non-conductive material, e.g. plastic. A nonconductive bracket 900 could increase the coil sensitivity of the coil 14, 72 to relative motion of other conductive target structures while a conductive bracket 900 could provide directional shielding to lessen the signal from the coil 14, 72 responsive to conductive door structures on the side of the bracket 900. A bracket could be made of both materials, for example, a steel part that is welded to the beam and a plastic part that is bolted to the steel part to provide for easy attachment of the coil and bracket to the beam.
For another example, referring to
The bending of the door beam 92 responsive to a crash is relatively consistent and predictable, wherein the amount of bending is proportional to total crash energy and the rate of bending is proportional to crash speed. The material properties of the door beam 92, e.g. relatively high yield strength, provide for relatively more uniform beam flexing sustained over significant beam bending. Furthermore, the strength and end mounting of the door beam 92 provides for relatively similar bending patterns regardless of the location on the door beam 92 where a crash force is applied. Abuse impacts to the door by lower mass, higher speed objects will generally cause the primary door beam 92 to deflect a small amount, but possibly at an initially high rate of speed. Abuse impacts to the door by higher mass, low speed objects may result in larger total main door beam 92 deflections, but at a substantially lower rate of the deflection. Mechanical abuse events can be ignored using a signal from the coil 14, 72—moving with the door beam 92—responsive to the inner panel 84 of the door 78. Although, the coil 14, 72 can be located almost anywhere along the door beam 92, locating the coil 14, 72 near the center third of the door beam 92 will provide the most consistent response. Also, locating the coil 14, 72 relatively near the center of the door beam 92 will provide for a more rapid displacement of the coil 14, 72 toward the inner panel 84 so as to provide a more rapid increase in the signal-to-noise ratio of the signal from the coil 14, 72 during a crash event. Rotation of the door beam 92 during the crash stroke, resulting from the off-axis inertia of the coil 14, 72 and its bracket 914, can be reduced by reducing the mass of the coil 14, 72 and bracket 914, and by locating their combined center of mass relatively close to the height of the center of the door beam 92, while avoiding interference with internal parts of the door 78. Furthermore, rotation of the door beam 92 and deflection of the bracket 914 during a relatively high acceleration of the door beam 92 during an ON crash event can be reduced if the bracket 914 attaching the coil 14, 72 to the door beam 92 is made of a relatively high stiffness but low mass material. Generally, a pole crash would engage the door beam 92 for almost any impact location along the door and most cars are designed so that the door beam 92 will engage the bumpers of regulatory MDB (Moving Deformable Barrier) impacts, making motion of the door beam 92 a reliable indicator of crash severity for many crash types.
Furthermore, the region below the door beam 92 in many doors 78 is relatively unused, often providing ample space for packaging a coil 14, 72 that will not conflict with existing/future door design and interior equipment. More particularly, in this location, the door window glass 910 would typically not constrain the placement of the coil 14, 72 relative to the surface(s) to be sensed, so the size (and cost) of the coil 14, 72 can be reduced and the coil-to-target initial distance can be optimized to give a larger signal (increased SNR) during the sensing time.
Yet further, a coil 14, 72 in cooperation with the inner panel 84 of the door 78 can provide for relatively less susceptibility to motion of metal inside the vehicle cabin in comparison with a coil operatively coupled to the inner panel 84 if near an access hole.
However, a system using a coil 14, 72 attached to the door beam 92 may be susceptible to delayed or inconsistent performance when an impacting vehicle has a bumper that is sufficiently high so as to not directly engage the door beam 92 during a collision therewith. Furthermore, vibration of the coil 14, 72 attached to the door beam 92 during operation of the vehicle may need to be controlled. For some door beam 92 cross-sectional profiles, for example, cross-sectional profiles that are not substantially curved or round, such as rectangular or square cross-sectional profiles, the associated door beam 92 may exhibit either unacceptable or unpredictable rotation during variable impacts such that a coil 14, 72 attached thereto may not provide a consistent and reliable signal for determining crash severity, particularly if the coil 14, 72 is not mounted sufficiently near the height of the center of the door beam 92.
The magnetic crash sensor 10.1iv, 10.1v may be adapted to sense both the motion of the outer skin 90 of the door moving towards the coil 14, 72 and the motion of the coil 14, 72 towards the inner panel 84, which would provide for a relatively rapid signal to “wake-up” the sensing system, provide a relatively quick indication of the speed of impact (e.g. rate of movement of the outer skin 90), and so as to provide a relatively more complex, feature-right signal that would be a superposition of signals responsive to both associated relative motions, but for which it is relatively more difficult to ascribe physical meaning to the associated response, and which would be more susceptible to mechanical abuse events of the vehicle.
Alternatively, magnetic crash sensor 10.1iv may be adapted to principally sense primarily only the relative motion of the door beam 92 relative to the inner panel 84, in which case, the coil 14, 72 would be magnetically shielded or decoupled from the outer skin 90, for example, by incorporating a magnetic shield (which, for example, may also include an eddy current shield as described herein above) into the bracket so as to reduce the magnetic communication between the coil 14, 72 and the outer skin 90 of the door 78 or by initially placing the coil 14, 72 substantially closer to the inner panel 84 than to the outer skin 90 so that motion of the outer skin 90 causes only a relatively small change in the signal from the coil 14, 72. Such an arrangement would be expected to provide a relatively delayed response during impact—relative to the arrangement that is adapted to also be responsive to the outer skin 90—but which would exhibit a relative high immunity to abuse events—e.g. that would either not cause significant total bending or would not cause a high bending rate of the door beam 92—whereby a crash could be discriminated responsive to an associated rate of motion in combination with a minimum or measure of total bending. Such an arrangement would provide for a relatively simple physical interpretation of the associated signals as being related to bending of the door beam 92 and the associated intrusion thereof towards the inner panel 84.
The conductive elements 86, 88 each comprise, for example, a thin metal sheet, film or coating, comprising either a paramagnetic or diamagnetic material that is relatively highly conductive, e.g. aluminum or copper, and which, for example, could be an integral part of the second portion 82 of the door 78. For example, the conductive elements 86, 88 could be in the form of relatively thin plates, a film, a tape (e.g. aluminum or copper), or a coating that is mounted on, applied to, or integrated with existing or supplemental structures associated with the inner panel 84 and the inside surface of the outer skin 90 of the door 78 respectively.
The frequency of the oscillator 98 is adapted so that the corresponding oscillating magnetic field generated by the at least one coil 14, 72 both provides for generating the associated eddy currents 102 in the conductive elements 86, 88, and is magnetically conducted through the ferromagnetic elements of the door 78 and proximate structure of the vehicle 12.
The at least one coil 14, 72 is responsive to both the first magnetic field 94 generated by the at least one coil 14, 72 and a second magnetic field 104 generated by the eddy currents 102 in the conductive elements 86, 88 responsive to the first magnetic field 94. The self-impedance of the coil 14, 72 is responsive to the characteristics of the associated magnetic circuit, e.g. the reluctance thereof and the affects of eddy currents in associated proximal conductive elements. Accordingly, the coil 14, 72 acts as a combination of a passive inductive element, a transmitter and a receiver. The passive inductive element exhibits self-inductance and self resistance, wherein the self-inductance is responsive to the geometry (coil shape, number of conductors, conductor size and cross-sectional shape, and number of turns) of the coil 14, 72 and the permeability of the associated magnetic circuit to which the associated magnetic flux is coupled; and the self-resistance of the coil is responsive to the resistivity, length and cross-sectional area of the conductors constituting the coil 14, 72. Acting as a transmitter, the coil 14, 72 generates and transmits a first magnetic field 94 to its surroundings, and acting as a receiver, the coil 14, 72 generates a voltage responsive to a time varying second magnetic field 104 generated by eddy currents in associated conductive elements within the surroundings, wherein the eddy currents are generated responsive to the time varying first magnetic field 94 generated and transmitted by the coil 14, 72 acting as a transmitter. The signal generated by the coil 14, 72 responsive to the second magnetic field 104 received by the coil 14, 72, in combination with the inherent self-impedance of the coil 14, 72, causes a complex current within or voltage across the coil 14, 72 responsive to an applied time varying voltage across or current through the coil 14, 72, and the ratio of the voltage across to the current through the coil 14, 72 provides an effective self-impedance of the coil 14, 72, changes of which are responsive to changes in the associated magnetic circuit, for example, resulting from the intrusion or deformation of proximal magnetic-field-influencing—e.g. metal—elements.
The at least one coil 14, 72 is operatively coupled to a signal conditioner/preprocessor circuit 114, which, for example, provides for preamplification, filtering, synchronous demodulation, and analog to digital conversion of the associated signal(s) therefrom, e.g. as described hereinabove. The signal conditioner/preprocessor circuit 114 is operatively coupled to a processor 116 which processes the signal therefrom, thereby providing for discriminating a crash, and controlling an associated safety restraint actuator 110—e.g. a side air bag inflator—operatively coupled thereto. More particularly, the signal conditioner/preprocessor circuit 114 provides for determining a measure responsive to the self-impedance of the at least one coil 14, 72 responsive to an analysis of the complex magnitude of the signal from the at least one coil 14, 72, for example, in relation to the signal applied thereto by the associated oscillator 98. For example, in one embodiment, the signal conditioner/preprocessor circuit 114, coil driver 96, oscillator 98 and processor 108 are incorporated in an electronic control unit 120 that is connected to the at least one coil 14, 72 with standard safety product cabling 122, which may include associated connectors.
In operation, the magnetic crash sensor 10.1iv, 10.1v provides a measure of the relative motion of the door beam 92 relative to the inner panel 84 and/or the outer skin 90 of the door 78, for example, as caused by a crushing of the outer skin 90 of the door 78 or the bending of the door beam 92 responsive to a side-impact of the vehicle 12. During non-crash conditions, an oscillating magnetic field resulting from the combination of the first 94 and second 104 magnetic fields would be sensed by the at least one coil 14, 72. If an object impacted the outer skin 90 of the door 78 causing a physical deflection thereof, then this oscillating magnetic field would be perturbed at least in part by changes in the second magnetic field 104 caused by movement or deformation of the associated first conductive element 80, 86 and the associated changes in the associated eddy currents 102 therein. If the impact is of sufficient severity, then the door beam 92 and the associated coil 14, 72 would also be moved or deformed thereby, causing additional changes in the associated eddy currents 102 in the first conductive element 80, 86 and the corresponding second magnetic field 104. Generally, the door beam 92 would not be significantly perturbed during impacts that are not of sufficient severity to warrant deployment of the associated safety restraint actuator 110, notwithstanding that there may be substantial associated deformation of the outer skin 90 of the door 78. Accordingly, in one embodiment, a magnetic crash sensor 10.1iv might incorporate the first conductive element 88, and not the first conductive element 86.
Responsive to a crash with an impacting object of sufficient energy to deform the at least one conductive element 80, changes to the shape or position of the at least one conductive element 80 relative to the at least one coil 14, 72, or vice versa, affect the magnetic field affecting the at least one coil 14, 72. A resulting signal is preprocessed by the signal conditioner/preprocessor circuit 114, which provides for measuring the signal across the at least one coil 14, 72 and provides for measuring the signal applied thereto by the associated coil driver 96. The signal conditioner/preprocessor circuit 114—alone, or in combination with another processor 116—provides for decomposing the signal from the at least one coil 14, 72 into real and imaginary components, for example, using the signal applied by the associated coil driver 96 as a phase reference.
Referring to
With the plurality of coil elements 14 connected in series, the current i through the series circuit 242, and the resulting detected signal 1038, is responsive associated sensed signal components from each of the coil elements L1′, L2′, L3′, L4′, . . . LK′, wherein each sensed signal component would correspond to the associated respective impedance Z1, Z2, Z3, Z4, . . . ZK of the respective coil element L1′, L2′, L3′, L4′, . . . LK′, wherein the associated respective impedances Z1, Z2, Z3, Z4, . . . ZK of the associated coil elements L1′, L2′, L3′, L4′, . . . LK′ are responsive to the associated respective magnetic field components 140.1, 140.2, 140.3, 140.4, . . . 140.k responsive to the associated interactions of the respective coil elements L1′, L2′, L3′, L4′, . . . LK′ with the respective different portions 20.1, 20.2, 20.3, 20.4 and 20.k of the vehicle 12. Accordingly, the detected signal 1038 provides for detecting a change in a magnetic condition of, or associated with, the vehicle 12, for example, as might result from either a crash or a proximate interaction with another vehicle. The plurality of coil elements are adapted to span a substantial region 1044 of a body or structural element 1046 of the vehicle 12, wherein the body or structural element 1046 of the vehicle 12 is susceptible to deformation responsive to a crash, or is susceptible to some other interaction with another vehicle that is to be detected. Accordingly, a detected signal 1038 responsive to the current i through the plurality of coil elements 14 distributed over a substantial region 1044 of a body or structural element 1046 of the vehicle 12, in a series circuit 242 driven by a time-varying voltage signal v across the series combination of the plurality of coil elements 14, provides for detecting from a single detected signal 1038 a change in a magnetic condition of, or associated with, the vehicle 12 over the associated substantial region 1044 of the body or structural element 1046 of the vehicle 12, so as to provide for a magnetic sensor 10 with relatively broad coverage.
In accordance with a fifth aspect 10.5 of the magnetic sensor 10, a plurality of response signals are measured each responsive to different coil elements L1′, L2′, L3′, L4′, . . . LK′ or subsets thereof. Referring to
Referring to
The at least one time-varying signal 1024 from the time-varying signal source 1020 may comprise either an oscillatory or pulsed waveform. For example, the oscillatory waveform may comprise a sinusoidal waveform, a triangular ramped waveform, a triangular sawtooth waveform, a square waveform, or a combination thereof, at a single frequency or a plurality of different frequencies; and the pulsed waveform may comprise any of various pulse shapes, including, but not limited to, a ramp, a sawtooth, an impulse or a rectangle, at a single pulsewidth or a plurality of different pulsewidths. Frequency diversity techniques can provide information about deformation depth or deformation rate of the associated different portions 20.1, 20.2, 20.3, 20.4 and 20.k of the vehicle 12 being sensed, and can also provide for improve electromagnetic compatibility and immunity to external electromagnetic noise and disturbances.
Referring to
Referring again to
Referring to
Referring to
The fourth through seventh aspects 10.4-10.7 of the magnetic sensor 10 provides for detecting deformation and/or displacement of associated at least one magnetic-field-influencing object 1064 constituting portions 20 of the vehicle 12 responsive to a crash, and/or provides for detecting the proximity or approach of an approaching or proximate external magnetic-field-influencing object 1064, within the sensing range of at least one coil elements 14 of the plurality of coil elements 14 distributed across either one-, two- or three-dimensional space. The plurality of coil elements 14 driven by at least one time-varying signal 1024 exhibit a characteristic complex impedance Z which is affected and changed by the influence of a proximate magnetic-field-influencing object 1064 and/or deformation or displacement of associated magnetic-field-influencing portions 20′ of the vehicle 12 in proximate operative relationship to coil elements 14 of the plurality of coil elements 14. Measurements of the voltage v across and current i through the coil elements 14 provide associated time varying sensed signals 1094 that provide for generating at least one detected signal 1038 responsive thereto and responsive to, or a measure of, the associated complex impedance Z of the associated plurality or pluralities of coil elements 14 or subsets 1078 thereof, which provides for a measure responsive to the dynamics of an approaching external magnetic-field-influencing object 1064, 1064′ (e.g. metal, metalized or ferromagnetic), or responsive to the dynamics of deformation of the at least one magnetic-field-influencing object 1064 constituting portions 20 of the vehicle 12 responsive to a crash, and which are in operative proximate relationship to the plurality or pluralities of coil elements 14 or subsets 1078 thereof. The time varying sensed signals 1094 are responsive to ferromagnetic and eddy current affects on the associated complex impedance Z of each of the associated plurality or pluralities of coil elements 14 or subsets 1078 thereof spanning a substantial region 1044 of a body or structural element 1046 to be sensed.
In accordance with an aspect of the magnetic sensor 10, either the geometry of first L1′ and at least second L2′ coil elements associated with different first 20.1 and at least second 20.2 portions of the vehicle 12, the associated at least one time-varying signal 1024, or an associated at least one detection process of an associated at least one detection circuit 32, are adapted so as to provide that a first response of the at least one detection circuit 32 to a first sensed signal component from a first coil element L1′ is substantially normalized—e.g. with respect to respective magnitudes or signal-to-noise rations of the associated sensed signal components—with respect to at least a second response of the at least one detection circuit 32 to at least a second sensed signal component from at least the second coil element L2′ for a comparably significant crash or proximity stimulus or stimuli affecting the first 20.1 and at least second 20.2 portions of the vehicle 12. Accordingly, in addition to being distributed over a region of space associated with an associated sensing region 1016, for an associated sensing region 1016 spanning different portions 20.1, 20.2, 20.3, 20.4 and 20.k of the vehicle 12 that are magnetically different in their associated influence on the associated plurality of coil elements 14, at least one of at least one geometry of the plurality of coil elements 14, the at least one time-varying signal 1024, and at least one detection process is adapted so that at least one of a first condition, a second condition and a third condition is satisfied so as to provide that a first response of the at least one detection circuit 32 to a first sensed signal component from a first coil element L1′ is substantially normalized with respect to at least a second response of the at least one detection circuit 32 to at least a second sensed signal component from at least the second coil element L2′ for a comparably significant crash stimulus or stimuli affecting the first 20.1 and at least second 20.2 portions of the vehicle 12.
The first condition is satisfied if the geometry—e.g. the size, shape, or number of turns—of the first L1′ and at least a second L2′ coil element are different. For example, referring to
The second condition is satisfied if a first time-varying signal 1024.1 operatively coupled to a first coil element L1′ is different from at least a second time-varying signal 1024.2 operatively coupled to at least a second coil element L2′. For example, referring to
The third condition is satisfied if a first detection process of the at least one detection circuit 32 operative on a first sensed signal component from or associated with a first coil element L1′ is different at least a second detection process of the at least one detection circuit 32 operative on at least a second sensed signal component from or associated with at least a second coil element L2′. For example, the associated signal gain associated with processing different signals from different coil elements 14 can be different, e.g. the signal from a coil element 14 of closer proximity to an associated first portion 20.1 of the vehicle 12 could be amplified less than the signal from a coil element 14 of further proximity to an associated second portion 20.2 of the vehicle 12, so that the affect on the detected signal 1038 of a change in the first portion 20.1 of the vehicle 12 is comparable to the affect on the detected signal 1038 of a change in the second portion 20.2 of the vehicle 12 for each change corresponding to a relatively similar crash or proximity stimulus or stimuli affecting the first 20.1 and at least second 20.2 portions of the vehicle 12.
Referring to
Referring to
Referring to
Referring to
Referring to
It should be appreciated that in any of the above magnetic crash sensor embodiments, that the circuitry and processes associated with
Referring to
The door 78—typically constructed with magnetically-permeable steel—has intrinsic magnetic properties. For example, the door 78 conducts magnetic flux, thereby enabling a permanent magnet to stick thereto. The hinges 2018 provide a relatively low reluctance path between the door 78 and the first pillar 2016. Moreover, the latch/lock mechanism 172′ and the striker 170, when engaged, provide a relatively low reluctance path between the door 78 and the second pillar 2024. Elsewhere, the door 78 is normally magnetically separated from the body 168 of the vehicle 12 by an associated air gap 2028. Accordingly, the hinges 2018 and striker 170 are magnetically connected by a first magnetic path 2030 along the door 78. Moreover, the first 2016 and second 2024 pillars—to which the hinges 2018 and striker 170 are respectively attached—are magnetically connected by a second magnetic path 2032—distinct from the first magnetic path 2030—comprising the body 168, structure 2034, or powertrain 2036 of the vehicle 12. Accordingly, the door 78 is part of a magnetic circuit 188 that is similar in nature to the core of a transformer, as illustrated in
The magnetic circuit 188 further comprises at least one first coil 2042 operatively connected to at least one first signal 2044, for example an oscillatory signal from an oscillator 2046. The at least one first coil 2042 is located at an associated at least one first location 2048, and responsive to the at least one first signal 2044 generates a magnetomotive force in the magnetic circuit 188 so as to generate a magnetic flux 186 therein. At least one magnetic sensing element 2050 is operatively connected to the magnetic circuit 188 at an associated at least one second location 2052 that is distinct from the at least one first location 2048. The at least one magnetic sensing element 2050 senses the magnetic flux 186, which is responsive to the magnetomotive force from the at least one first coil 2042 and to the magnetic properties of the magnetic circuit 188.
For example, as illustrated in
The first signal 2044 comprises a sinusoidal voltage generated by an oscillator 2046 comprising a crystal stabilized (i.e. substantially drift-free) TTL square wave signal generated by a microprocessor 2056 and subsequently filtered by a band-pass filter. The signal from the oscillator 2046 is fed to a coil driver 2058—for example, through a buffer amplifier.
The oscillation frequency of the oscillator 2046 is selected, as a function of the expected noise sources, to enhance system performance. For example, a frequency different from that of AC power lines (e.g. 60 Hz) could be chosen to avoid interference therefrom. Ultrasonic frequencies appear to be useful. The permeability of typical automotive steel is frequency dependent with a bandwidth of about 100 KHz. The frequency range of the permeability of the associated magnetic circuit 188 can likely be extended to 1 MHz or higher by adding materials such as ferrite or mu-metal thereto.
The skin depth of the magnetic flux 186 is responsive to frequency, so the depth of the magnetic flux 186 in the door 78 and the shape and reach of the associated proximity field can be varied by changing the oscillation frequency (or frequencies). The oscillator 2046 may be modulated either in amplitude, frequency, or by bursting.
Each at least one first coil 2042 is driven by an associated coil driver 2058 that provides sufficient power at an impedance compatible with the first coil 2042 so that the resulting magnetic flux 186 is sufficiently strong to be detected by the at least one magnetic sensing element 2050. The coil driver 2058 is also, for example, provided with short circuit protection and is operated so as to avoid saturation or clipping of the first signal 2044. The coil driver 2058 is designed to operate in an automotive environment, for example to operate over a associated range of possible battery voltages. The first signal 2044 from the coil driver 2058 may, for example, be either a voltage signal or a current signal.
The coil driver 2058 drives the first coil 2042 through a sense/test circuit 2060. The sense/test circuit 2060 senses either a current or voltage from the first coil 2042, or a signal from a supplemental sense coil 2062, or a combination of the three, to confirm or test the operation of the first coil 2042. This also provides a continuous test of the integrity of the door 78. For example, a supplemental sense coil 2062 would directly sense the magnetic flux 186 generated by the first coil 2042. The sense/test circuit 2060 may also, for example, test the first coil 2042 for an open or short so as to improve the reliability of the magnetic sensor 2010, particularly when used to control the actuation of a safety restraint actuator 110, so as to prevent a false deployment or a failure to deploy when necessary. The integrity, or health, of the at least one first coil 2042 is, for example, tested every measurement cycle.
A plurality of first coils 2042 may be driven separately, as illustrated in
The sense/test circuit 2060 also provides a measure of the power delivered to the first coil 2042 so that the magnetic flux 186 coupled to proximate metal objects can be estimated. For example, a steel object such as another vehicle proximate to the door 78 provides an alternate path for magnetic flux 186 from the at least one first coil 2042, which affects the magnetic circuit 188 and the reluctance seen by the at least one first coil 2042, thereby changing the load on the at least one first coil 2042, which changes the power provided thereto by the coil driver 2058. Generally, a portion of the magnetic flux 186 generated by the at least one first coil 2042 is coupled within the magnetic circuit 188, and a portion bypasses the magnetic circuit 188, whether via an alternate magnetic path or by radiation. The portion of magnetic flux 186 that bypasses the magnetic circuit 188 increases the load upon the coil driver 2058, which increase is sensed by a bypass power processor 2066 using measurements from the sense/test circuit 2060 of the voltage across and the current through the at least one first coil 2042. For a plurality of first coils 2042, the bypass power processor 2066 can provide a measure of direction to a proximate magnetic-field-affecting object from the separate measurements of the associated separate sense/test circuits 2060.1 and 2060.2, particularly from a measure of the difference in currents flowing to the separate first coils 2042.1 and 2042.2 for a given common drive voltage.
The at least one magnetic sensing element 2050 is responsive to the magnetic flux 186 at the second location 2052, including both a first portion of magnetic flux 186 that is conducted through the door 78, and a second portion of magnetic flux 186, i.e. leakage flux, that bypasses at least a portion of the door 78—for example as a result of an object, such as another vehicle proximate to the door 78, that couples magnetic flux 186 from the at least one first coil 2042 to the at least one magnetic sensing element 2050.
An output from the at least one magnetic sensing element 2050 is operatively connected to a preamplifier/test circuit 2068 which, for example, buffers the magnetic sensing element 2050 from loading by the subsequent circuitry and provides a relatively low impedance output so as to reduce noise. The preamplifier/test circuit 2068 also amplifies the signal from the at least one magnetic sensing element 2050 to a level sufficiently high to permit appropriate signal processing and demodulation before subsequent analog-to-digital conversion for processing by the microprocessor 2056. The microprocessor 2056 gathers data, monitors system health and integrity, and determines whether or not to actuate the safety restraint actuator 110.
The preamplifier/test circuit 2068 also monitors the integrity of the magnetic sensing element 2050, for example by comparing the signal therefrom with “expected” levels and expected wave shapes (e.g. a sinusoidal shape). This provides a continuous test of the integrity of the magnetic sensing element 2050 and the magnetic transfer function property of the door 78. The preamplifier/test circuit 2068 may also, for example, test the at least one magnetic sensing element 2050, for example a second coil 2054, for an open or short so as to improve the reliability of the magnetic sensor 2010, particularly when used to control the actuation of a safety restraint actuator 110, so as to prevent a false deployment or a failure to deploy when necessary. The integrity, or health, of the at least one magnetic sensing element 2050 is tested every measurement cycle.
The magnetic sensing element 2050 senses from the magnetic flux 186 proximate thereto a sinusoidal carrier that is modulated responsive to the reluctance of the magnetic circuit 188. This signal from the magnetic sensing element 2050 is amplified by the preamplifier/test circuit 2068, and a synchronous demodulator 2070 operatively connected thereto extracts the modulation signal from the sinusoidal carrier, which modulation signal contains a bent metal signal component 2072 and a proximity signal component 2074. The bent metal signal component 2072 is responsive to the magnetic flux 186 conducted through the metal of the door 78. The proximity signal component 2074 is responsive to the leakage magnetic flux 186 that is coupled between the at least one first coil 2042 and the magnetic sensing element 2050 along a path that bypasses the metal of the door 78. The difference in the relative strengths of the bent metal signal component 2072 and a proximity signal component 2074 is dependent upon the difference in permeances of the associated magnetic flux paths.
A bent metal processor 2076 DC couples—with, for example, unity gain—the bent metal signal component 2072 to the microprocessor 2056 through an A/D converter 2078.1. The bent metal signal component 2072 is responsive to the time rate of change of magnetic flux 186 in the door 78. Relatively slow signals of relatively low amplitude correspond to non-deployment events for which a safety restraint actuator 110 should not be deployed, for example a low speed impact of the door 78 by a shopping cart. Relatively fast signals of relatively large amplitude correspond to deployment events for which a safety restraint actuator 110 should be deployed, for example an impact of the door 78 by a pole or barrier (e.g. an FMVSS-214 condition). During a pole crash, the steel of the door 78 becomes magnetically shorted to the adjacent body, thereby magnetically shorting the flux path—as a result of either the magnetic influence of a proximate magnetic object (e.g. a steel pole), or by the physical affect of the impact on the associated magnetic circuit 188—which significantly reduces the magnetic flux 186 sensed by a magnetic sensing element 2050 at the striker 170. The magnetic sensing element 2050 is responsive to those changes to the magnetic circuit 188 which either increase or decrease the associated magnetic flux 186 sensed thereby.
The proximity processor 2080 amplifies the proximity signal component 2074 from the synchronous demodulator 2070 by some gain factor based on coil geometry and vehicle structure, and DC couples the amplified signal through an A/D converter 2078.2. The proximity signal component 2074 is responsive to the time rate of change of magnetic flux 186 that bypasses door 78. Notwithstanding a greater susceptibility to noise in comparison with the bent metal signal component 2072, the proximity signal component 2074 enables the detection of metallic (particularly ferromagnetic) objects that are approaching the door 78, for example a vehicle approaching at high speed or a vehicle in an adjacent lane of traffic. Another vehicle approaching the door 78 on a collision course therewith is indicated by a relatively fast signal, for which a safety restraint actuator 110 would be deployed upon impact if followed by a corresponding bent metal signal component 2072.
Accordingly, if the rate of change of the proximity signal component 2074 is greater than a first threshold, then the safety restraint actuator 110 is deployed when the bent metal signal component 2072 exceeds a second threshold and the rate of change thereof exceeds a third threshold. Otherwise, if no bent metal signature follows, for example if the proximity signal component 2074 had resulted from a passing vehicle, then the system stands down.
The above described magnetic sensor 2010 can be embodied in various ways. The particular circuitry, whether analog, digital or optical is not considered to be limiting and can be designed by one of ordinary skill in the art in accordance with the teachings herein. For example, where used, an oscillator, amplifier, logic element, modulator, demodulator, A/D converter can be of any known type, for example using transistors, for example field effect or bipolar, or other discrete components; integrated circuits; operational amplifiers, or logic circuits, or custom integrated circuits. Moreover, where used, a microprocessor can be any computing device.
In accordance with the theory of magnetic circuits and transformers, magnetic lines of flux always close on themselves and preferably follow a path of least magnetic resistance, for example so as to follow the path of ferromagnetic materials, such as steel or ferrite materials. Moreover, changes in area or permeability along the magnetic circuit cause a leakage of magnetic flux 186 proximate thereto, which leakage is also known as fringing. A magnetic circuit 188 is characterized by a reluctance , wherein the amount of magnetic flux φ in a magnetic circuit for a given magnetomotive force F is given by φ=F/. The reluctance of a series magnetic circuit is given by the sum of the respective reluctances of the respective elements in series. The reluctance of an air gap is significantly greater than that of a ferromagnetic material, and as a result, the magnetic flux leaks into the space surrounding the air gap, forming a leakage field. A ferromagnetic object entering the leakage field provides an alternate path for the magnetic flux, thereby bypassing the air gap and affecting the reluctance of the magnetic circuit 188. Stated in another way, the leakage flux field changes shape so that the ferromagnetic object becomes part of the magnetic circuit 188.
As illustrated in
A first coil 2042 has a self-inductance which has one value when the first coil is in free space, and another when the coil is operatively connected to a magnetic circuit 188, for example by wrapping the first coil 2042 around a portion of the magnetic circuit 188. In the latter case, the self inductance of the first coil 2042 is dependent upon the magnetic properties of the magnetic circuit 188. Moreover, the magnetic properties of the magnetic circuit 188 are altered if the magnetic circuit 188 is physically deformed, or if ferromagnetic elements are brought in proximity with the magnetic circuit 188, particularly in proximity with the leakage fields thereof. Accordingly, a deformation of the door 78 or the approach of another vehicle to the door 78 are both examples of perturbations to the magnetic properties of the magnetic circuit 188, both of which can be detected by either a change in inductance of the first coil 2042, or by a change in the magnetic coupling between a first coil 2042 at a first location 2048 and a magnetic sensing element 2050 for sensing the magnetic flux 186 in the magnetic circuit 188 at a second location 2052 distinct from the first location 2048.
In operation, the at least one first signal 2044 operatively coupled to the associated at least one first coil 2042 by the associated at least one coil driver 2058 causes a current flow in the at least one first coil 2042 which generates a magnetic flux 186 therein, which in turn generates a magnetic flux 186 in the magnetic circuit 188 to which the at least one first coil 2042 is coupled. The magnetic flux 186 is conducted by the door 78, which is a part of the magnetic circuit 188. The at least one first signal 2044 comprising an oscillating signal, for example a sinusoidal voltage or current excitation, is applied to at least one first coil 2042 operatively coupled to a hinge 2018 of a door 78. Referring to
The at least one first signal 2044 from the oscillator 2046 is amplified by the associated at least one coil driver 2058 and operatively coupled to the at least one first coil 2042 through an associated sense/test circuit 2060. The at least one first coil 2042 generates a magnetic flux 186 in the magnetic circuit 188, particularly the door 78, and at least a portion of the magnetic flux 186 is sensed by the magnetic sensing element 2050, for example by a second coil 2054 wrapped around the striker 170.
The magnetic flux 186 travels through the magnetic circuit 188, particularly the ferromagnetic portions thereof including those of the portions of the vehicle 12, such as the door 78, that are monitored by the magnetic sensor 2010. A first portion 2086 of the magnetic flux 186, known herein as the bent metal flux component 2086, passes through the ferromagnetic elements of the magnetic circuit 188 and is sensed by the magnetic sensing element 2050, which provides a first signal component 72 known herein as a bent metal signal component 2072 that is responsive thereto, or in other words, that is responsive to changes of the magnetic characteristics of the magnetic circuit 188. The magnetic flux 186 seeks to travel inside the steel structure of the door 78. More magnetic flux 186 automatically enters those parts of the steel that are thicker, which would likely correspond to those elements of the door structure that add strength to the door 78. Where the steel is thinner, the magnetic flux density is correspondingly reduced. Stated in another way, the magnetic flux 186 travels in ratiometric proportion with the cross-sectional area of the steel. The magnetic flux 186 is generally not present in the plastic parts other than as a result of leakage elsewhere in the magnetic circuit 188, however, for a steel door 78, these parts are generally not structural. Accordingly, the magnetic sensor 2010 generates magnetic flux 186 that passes through the structural elements of the door 78, and is responsive to mechanical changes to these structural elements to a degree that those mechanical changes influence the magnetic flux 186.
A second portion 2088 of the magnetic flux 186, known herein as the proximity flux component 2088, extends outside the physical extent of the magnetic circuit 188 and is sensed by the magnetic sensing element 2050, which provides a second signal component 2074 known herein as a proximity signal component 2074 that is responsive thereto, or in other words, that is responsive to changes of the magnetic characteristics of a region proximate to the magnetic circuit 188.
Changes to the size, shape, position, construction integrity, spot-weld quantity and integrity, material correctness, and assembly alignment of the door 78; or to the magnetic environment proximate to the door 78, for example, by the presence of a ferromagnetic object such as another vehicle 2090; affect the magnetic circuit 188, and thereby affect magnetic flux 186 sensed by the magnetic sensing element 2050.
The door 78, or another part of the magnetic circuit 188 subject to surveillance, may be supplemented or modified by adding or relocating steel or other highly permeable material in the door 78 to as to modify the strength and/or shape of the respective first 2086 and second 2088 portions of the magnetic flux 186, thereby enhancing the associated magnetic circuit 188 so as to improve the respective bent metal 2072 and/or proximity 2074 signal components. This may further enable a reduction in power to at least one coil driver 2058, thereby reducing associated radiated power from the at least one first coil 2042. Moreover, this may enable a reduction in gain of the associated preamplifier/test circuit 2068, which improves the associated signal-to-noise ratio. The magnetic flux 186 generally follows a path of least reluctance, which typically would correspond to sections of greatest amounts of magnetically permeable material. For a door 78 constructed of steel, this path would then correspond to one or more sections of the door 78 that contribute substantially to the strength of the door 78. Accordingly, the magnetic circuit 188 can be optimized with respect to magnetic performance, strength and cost by this supplementation or modification of the associated magnetically permeable material.
For example, the magnetic circuit 188 can be modified or augmented in various ways, including but not limited to the following, many of which provide for increasing the ratio of magnetic flux density per unit drive current and thereby increase the magnetic efficiency of the magnetic circuit 188:
-
- 1. Mu-metal, ferrite or some other magnetic conductor can be added to the door 78, for example to a plastic door 78, e.g. by coating the inside of the door 14 with a ferrite paint or coating to increase the permeability thereof, to augment or re-tune the door's natural magnetic characteristic;
- 2. Holes may be added to the door 78 or modified, thus shifting the magnetic conduction;
- 3. A supplemental ferrite or mu-metal flexible linkage may be added between the “A” pillar 184 and the door 78 for generating the magnetic flux 186, instead of the hinges 2018;
- 4. Ferrite, an amorphous metal (e.g. METGLAS®), or mu-metal may be placed in the striker 170 and second coil 2054, or generally added to or used as the core of either the first 2042 or second 2054 coil to enhance the magnetic flux 186 therein, or to provide for operating at a lower current level for the same amount of magnetic flux 186;
- 5. A permanent magnet may be added to the door 78 to augment or re-tune the intrinsic permanent magnetic characteristic signal of the magnetic circuit 188;
- 6. The magnetic structure of the door 78 can be changed, for example by using a thinner metal skin, a plastic door skin, or ferrite rods to change the magnetic gain, so as to enhance proximity sensing for enhanced system safing responsive to the proximity flux component 2088;
- 7. The hinge or striker shape, size, or material can be changed to improve their associated magnetic characteristics; and
- 8. The door side-guardrail assembly and construction, the hinge assembly, or the latch/lock mechanism/striker assembly can be changed to enhance system performance and sensitivity.
In addition to the herein described use in detecting a crash or an impending crash, the magnetic sensor 2010 can also be used to monitor the structural integrity of structural elements of the magnetic circuit 188, particularly the structural integrity of the door 78, for example as a post manufacturing inspection of a door 78 either mounted to a vehicle 12, or separate therefrom in a magnetic circuit of an associated test apparatus. For example, a missing structural element, such as guard rail, or poor spot welds, would likely affect the reluctance of the door 78 and if so, could be detected prior to assembly. Stated another way, a steel door 78 that does not conduct magnetic flux 186 well would not likely have sufficient side-impact strength. Accordingly, the door 78 can be tested for proper magnetic integrity, which can be predictive of the performance of the magnetic sensor 2010, and indicative of the ability of the door 78 to withstand impact and thereby protect an occupant therefrom.
The magnetic sensing element 2050 is responsive to a superposition of the first 2086 and second 2088 portions of magnetic flux 186, and converts the composite of both portions to a voltage that is amplified by the preamplifier/test circuit 2068, wherein the relative strengths of the associated bent metal 2072 and proximity 2074 signal components is in proportion to the associated relative strengths of the first 2086 and second 2088 portions of magnetic flux 186. The magnetic sensing element 2050 may be Faraday shielded to reduce noise, wherein a Faraday shield would shield the magnetic sensing element 2050, e.g. second coil 2054, from stray electric fields so as to prevent or reduce noise in the signal therefrom. For a magnetic sensing element 2050 comprising a second coil 2054, for example around the striker 170, the second coil 2054 may be also be parallel resonated to match the associated carrier frequency of the at least one first signal 2044 so as to improve the associated signal-to-noise ratio. Parallel resonance of the second coil 2054 provides for increasing the strength of the signal therefrom, and for increasing the sensitivity thereof to variations in the magnetic flux 186 in the magnetic circuit 188. Experiments have shown that locating the second coil 2054 proximate to the end wall 2092 of the door 78 enhances the awareness of the proximity flux component 2088 of the magnetic flux 186. This suggests that the latch/lock mechanism 172′—a localized thickening of the door metal—may act be as a magnetic lens to magnify the effect of the proximity flux component 2088 at the second coil 2054. The air gap 2028 helps to create the proximity flux component 2088, and the region of greatest sensitivity by the proximity flux component 2088 to approaching objects is proximate to the air gap 2028. Impacts to the door 78 tend to modulate the air gap 2028, causing significant changes to the associated magnetic flux lines 2084, thereby causing the magnetic sensing element 2050 to generate an associated signal of significant magnitude. The signal responsive to the modulated air gap 2028 provides a measure of instantaneous recoil velocity of the door 78, which may be used to detect door bounce events for which an associated safety restraint actuator 110 is typically not deployed. The magnetic sensor 2010 can be responsive to movement of a latched door 78,
More particularly, the door 78 acts as a rigid body at the beginning of a collision and is pushed inwards towards the body of the vehicle 12 against the compliance of the weatherseal surrounding the door 78, thereby exhibiting elastic behavior. The magnetic flux 186 sensed by the magnetic sensing element 2050 changes responsive to the movement of the door 78, thereby enabling the lateral position and velocity of the door 78 to be measured from that change.
If the momentum of the impact is less than a threshold, for example for small objects or low impact velocities, the door 78 will then bottom out within a range of elastic behavior and rebound, thereby reversing the above described change to the magnetic flux 186 which is indicated by a shift in polarity of the signal from the magnetic sensing element 2050. Accordingly, the detection of such a rebound event is indicative of an impact for which the safety restraint actuator 110 would not be necessary. Otherwise, if the momentum of the impact is greater than a threshold, then the door 78 becomes plastically deformed, resulting in a significant change to the bent metal signal component 2072, which can be indicative of a need to subsequently deploy the safety restraint actuator 110. Accordingly, if after an initial movement of the door 78 is detected, either the door 78 fails to rebound and/or a significant bent metal signal component 2072 is detected, then the impact might be considered to be sufficiently severe to warrant the deployment of the safety restraint actuator 110. Moreover, the initial velocity of the door 78 can be used as a predictor or indicator of impact severity.
A ferromagnetic door 78 is characterized by an associated natural permanent magnetic field which acts to generate a static magnetic flux 186 within the magnetic circuit 188 responsive to the reluctance of the magnetic circuit 188, changes to which as a result of door motion are sensed by the magnetic sensing element 2050. This response—effectively an AC transformer transfer component—is superimposed upon the response to the at least one first signal 2044, and can provide an independent measure of door motion and impact velocity.
Experiments have shown that responsive to an FMVSS-214 impact the door 78 can rotate about its centerline causing—at the beginning of the impact—an increase in the air gap 2028 between the door 78 and the vehicle body at the top of the door 78. By comparison, experiments have shown that a pole-type impact causes a corresponding reduction in the air gap 2028. Accordingly, the behavior of the air gap 2028 responsive to a crash can be used to identify the type of crash. Accordingly both the type and severity of the crash can be detected by the magnetic sensor 2010. Commencing with an impact, the door 78 is generally moves readily responsive to the crash until the latch/lock mechanism 172′ bottoms out against the associated striker 170. Accordingly for a striking object that is relatively massive in comparison with the door 78, the velocity of impact can be measured by the magnetic sensor 2010 from the motion of the door 78 prior to this “bottoming out” thereof. After the door 78 “bottoms out” against the vehicle body, the impact causes bending or deformation of the door 78, causing further changes to the magnetic circuit 188 that are sensed by the magnetic sensor 2010, providing further information about the intensity and duration of the crash.
Another vehicle 2090 proximate to the at least one first coil 2042 attracts magnetic flux 186, thereby causing a third portion 2094 of the magnetic flux 186 generated by the at least one first coil 2042 to bypass the magnetic sensing element 2050. Moreover, if the door 78 becomes dented or deformed, the distribution and/or strength of the magnetic flux 186 in the door 78 changes, which change is sensed either by the magnetic sensing element 2050 or by a change in the load upon the at least one first signal 2044 by the at least one first coil 2042. Accordingly, substantially the entire door 78 acts a sensing element of the magnetic sensor 2010, wherein the effect of changes to the magnetic characteristics thereof on the number and distribution of the magnetic flux lines 2084 propagates at the speed of light from the location of the disturbance to either the at least one first coil 2042 or the magnetic sensing element 2050. Moreover, by placing the at least one first coil 2042 on at least one hinge 2018, and the second coil 2054 on the striker 170, the door 78 becomes a sensing element without actually running any wires or signal cables into the door 78. The magnetic sensor 2010 using the door 78 as a sensing element in a proximity sensing mode can be used to either monitor a blind spot of the vehicle 12 or to monitor traffic in an adjacent lane. The extent of coverage by the proximity mode can be increased by increasing the strength of the associated magnetic flux 186, e.g. by increasing the current supplied to the first coil 2042, or by adapting the associated magnetic circuit 188 to increase the associated proximity flux component 2088.
With substantially the entire door 78 as a sensor, the magnetic sensor 2010 can sense incoming objects approximately of door dimension. Car bumpers and roadside poles similar to the door dimension, for which a safety restraint actuator 110 would be required in a crash, will generally be visible whereas basketball and other small objects, for which a safety restraint actuator 110 would not be required, would be less visible. A shopping cart loaded with groceries would also be visible to the magnetic sensor 2010, however the decision of whether or not to deploy a safety restraint actuator 110 would be based upon more factors than just the visibility of a particular object. The magnetic sensor 2010 is not responsive to impacts such as impacts to the undercarriage, for example from a rock, that do not affect the magnetic circuit 188, but which might otherwise affect an acceleration based crash sensor.
Accordingly, the magnetic sensor 2010 is responsive to various physical effects upon the magnetic circuit 188, including but not limited to the following:
-
- 1) Changes to the air gap 2028 of the magnetic circuit affecting the bent metal signal component 2072.
- 2) Changes in the shape and density of the proximity flux component 2088 proximate to the air gap 2028 surrounding the door 78, including the front edge of the door 78 and front fender, the rear edge of door 78 and rear fender (or the rear door 78 of a four (4) door vehicle), the bottom of the door 78 to floor board, and, to a lesser extent, the top of the door 78 or window frame to the roof. The bent metal signal component 2072 is responsive to deformations of the door 78 or adjacent body components that close, or short, the air gap 2028.
- 3) The door 78, particularly the skin thereof, has a natural resonant frequency that can be excited by the at least one first coil 2042 if driven at that frequency the at least one first signal 2044. An impact to the door 78 induces vibrations therein associated with the resonant frequency thereof, and with associated overtones. At this resonant frequency, if the vibrating elements of the door 78 become constrained as by contact with an impacting object, this causes a dampening of the resonance which increases the eddy current losses in the magnetic circuit 188, which can be measured by the bypass power processor 2066 from the power supplied to the at least one first coil 2042. Furthermore, the impacting object can influence the associated resonances, so that the nature of the resonances measured by the magnetic sensor 2010 provides associated information about the nature of the impact—e.g. severity—or the nature of the impacting object. Stated in another way, the door 78 has a natural resonant behavior, but exhibits a forced response to the impact thereof by an impacting object because of the continued interaction of the impacting object with the door 78.
- 4) The structural elements of the door 78 typically provide a path of least reluctance for the associated magnetic flux 186, and mechanical stresses therein can alter the reluctance thereof, so that changes to the magnetic flux 186 can be related to the level of forces applied to the door 78 and to the structural elements thereof, which force levels can be related to the momentum or velocity of the impacting object. Accordingly, the measurements of the magnetic flux 186 provides a measure of threat to the door 78.
The bent metal 2072 and proximity 2074 signal components in the composite signal from the magnetic sensing element 2050 are demodulated by the synchronous demodulator 2070 and amplified by different respective gains of the associated bent metal 2076 and proximity 2080 processors, wherein the respective gains are for example in proportion to the relative permeance of the materials associated with the respective magnetic flux components. The bent metal 2072 and proximity 2074 signal components differ with respect to signal magnitude, and without further differentiation, only one of the two components would be useful at a given time. Prior to impact, the proximity signal component 2074 provides information about a proximate object. However, after the occurrence of an impact, the proximity signal component 2074 becomes relatively small, if not insubstantial, in comparison with the corresponding bent metal signal component 2072. For example, the proximity signal component 2074 might have a magnitude of 0.2 volts, which is about twenty five times smaller than the corresponding bent metal signal component 2072 after impact, which might have a magnitude of 5.0 volts. For example, when the bent metal signal component 2072 is of sufficient magnitude to indicate a physical disturbance of the magnetic circuit 188, then the proximity signal component 2074 would be saturated. Otherwise, the bent metal signal component 2072 would be of negligible magnitude and the proximity signal component 2074 would be useful for detecting objects proximate to the door 78. This mutual exclusive utility of the respective signal components is consistent with the sequence of a crash, in that an impacting object becomes proximate to the vehicle 12 before impacting the door 78; and after the impact has occurred as indicated by the bent metal signal component 2072, there would likely be little need to continue to detect the proximity signal component 2074.
Given the bent metal 2072 and proximity 2074 signal components, the microprocessor 2056 can monitor the total magnetic health of the door 78 and be aware of relatively large metal objects in proximity thereto. An example of one algorithm using this information to control a safety restraint actuator 110 would be to monitor the proximity signal component 2074 to detect a relatively rapid approach of a relatively large metal object. When the proximity signal component 2074 becomes saturated, indicating a likely perturbation to the physical magnetic circuit 188, then if the bent metal signal component 2072 indicates a sufficiently large change, then it is assumed that a potentially injurious impact has occurred and the safety restraint actuator 110 would be actuated. Otherwise, if the proximity signal component 2074 returns to a quiescent state without the occurrence of a significant bent metal signal component 2072, then it is assumed that the door 78 has not been impacted, but instead, for example, another vehicle has passed by the door 78, and the safety restraint actuator 110 would not be actuated.
Both the power applied to the at least one first coil 2042, and the gain and phase of the signal from the magnetic sensing element 2050 in relation to the at least one first signal 2044, are continuously monitored and stored in a memory 2095 of a microprocessor 2056 as a real-time magnetic signature of the door 78. In an embodiment of the magnetic sensor 2010 responsive to relative phase, the phase of the signal from the magnetic sensing element 2050 can be compared with that of the first signal 2044 from the oscillator 2046 with a phase detector 2096 which outputs the associated phase difference to the microprocessor 2056. The real-time magnetic signature is compared with at least one other comparable magnetic signature—for example at least one magnetic signature representing the door 78 prior to an impact or collision, i.e. a normal signature; or at least one magnetic signature representing various impacts or crashes—in order to determine if an associated safety restraint actuator 110 should be actuated. The at least one normal signature may include magnetic signatures that account for variations in the magnetic flux 186 as a result of either metal objects proximate to or approaching the door 78 or variations as a result of corrosion or variations in temperature. The normal signature may be updated over time so as to track minor perturbations of the door 78, such as due to temperature or corrosion, which changes would likely occur relatively slowly over time. If the real-time magnetic signature of the bent metal signal component 2072 is sufficiently different from the normal magnetic signature, the microprocessor 2056 would actuate the safety restraint actuator 110.
Accordingly, the magnetic sensor 2010 is responsive to both small-signal and large-signal disturbances. Small-signal disturbances would include, for example, impacts by relatively small objects such as basketballs or other sporting projectiles, which typically do not cause plastic deformation of the door 78, but for which the door 78 and surrounding weather-seal respond elastically. Large-signal disturbances would include, for example, side impacts that causes plastic deformation of the door 78, thereby permanently shifting its magnetic signature. The magnetic sensor 2010 detects the change in magnetic signature from the pre-impact undeformed condition to the post-impact deformed condition. Moreover, the plastically deformed metal is work hardened which causes a change to the permeance thereof, which is sensed by the magnetic sensor 2010. At the beginning of the impact, prior to plastic deformation of the door 78, the magnetic sensor 2010 is able to estimate the impact velocity and severity of the impact using principles of the physics of collisions including conservation of energy and momentum, whereby the response of the door 78 increases with increasing impact severity. The signal from the magnetic sensing element 2050 comprises information about both the instantaneous position and the instantaneous velocity of the door 78. Moreover, particular polarities of the signal are indicative of particular motions of the door 78.
The magnetic sensor 2010 provides a real-time validation of the health and integrity of the respective at least one first coil 2042 and the second coil 2054, by testing the respective coils for shorts or open conditions, or by using a separate sense coil 2062 to detect the magnetic flux 186 generated by the at least one first coil 2042. Moreover, the magnetic sensor 2010 provides a continuous test of the integrity of the magnetic circuit 188, including the component under magnetic surveillance, for example the door 78.
Referring to
Referring to
The at least one first coil 2042 or the at least one magnetic sensing element 2050 can be located at a variety of locations and constructed in accordance with a variety of configurations, including but not limited to the following: one or more hinges; the striker; the side impact protection rail or beam inside the door 78; around or proximate to the latch/lock mechanism either inside or outside the door 78; inside the spot weld line on the top or bottom of the door 78; around or proximate to the hinge bolts; on the inner door skin of a plastic or steel door 78 with the perimeter of the coil nearly matching the perimeter of the door 78; around the window glass perimeter; around the entire door structure such as in the air gap surrounding the door 78 and the opening that one passes through when entering or exiting the vehicle; in a window such as the driver-side window, as a defroster; behind a plastic door handle or trim component, along with associated electronics; around the window glass opening in the door 78 through which the window is lowered; or in the plastic side view mirror housing for sensing over an extended range, for example to locate steel objects that might pose a side-impact threat.
The magnetic fields generated by these arrangements have a variety of principal orientations, including but not limited to longitudinal, transverse, and vertical. For example, a first coil 2042 can be placed around a hinge 2018 so that the associated magnetic field is either longitudinal or transverse, the former arrangement providing principally a bent metal flux component 2086, whereas the later arrangement providing a relatively strong proximity flux component 2088. As another example, a first coil 2042 around the window glass opening in the door 78 through which the window is lowered generates a vertical magnetic field that circulates around the vehicle along a transverse section thereof. As yet another example, a first coil 2042 around the door 78 or window in the plane thereof generates a transverse magnetic field that is useful for proximity sensing. Different first coils 2042, at least one adapted to produce principally a bent metal flux component 2086 and the other adapted to produce principally a proximity flux component 2088 can be used with different associated first signals 2044, for example, respective first signals with different oscillation frequencies, so as to provide distinguishable bent metal 2072 and proximity 2074 signal components in the signal from the magnetic sensing element 2050, wherein the respective signals would be demodulated by respective synchronous demodulators 2070. For example, in one embodiment, a 10 KHz first signal 2044.1 is applied to a first coil 42.1 on the top hinge 2018.1, and a 20 KHz first signal 2044.2 is applied to a first coil 42.2 on the bottom hinge 2018.2, and both frequencies are sensed substantially simultaneously by different associated magnetic sensing elements 2050 associated with the B-pillar and C-pillar of the vehicle 12, respectively.
The operating point of the magnetic sensor 2010, for example the level of magnetic flux 186 within the magnetic circuit 188 and the nominal current supplied to the at least one first coil 2042, under quiescent conditions, can be adjusted by adjusting the wire gage or number of turns of at least one first coil 2042.
The system safing or proximity detection can be enhanced by various means, including but not limited to placing a winding around the undercarriage, door opening, or hood of the automobile; placing a winding around the front fender of the automobile; placing a ferrite rod inside the hinge coil, or inside the striker coil for magnetic focusing; placing a ferrite rod coil in the gap or space between the doors; or placing a supplemental first coil 2042 in the side-view mirror molding, which extends sidewards away from the vehicle. An additional system safing supplemental first coil 2042, with proper phasing and with the magnetic circuit return properly adjusted, would substantially increase the system safing signal performance. For example, this coil could be about 3 inches in diameter and in a plane parallel to the door surface, or wound on a ferrite rod aligned to enhance the launch range and enhance the directivity for system safing. Moreover, by the combination of proximity detection and bent metal detection, together with a self-test of the associated at least one first coil 2042 and the magnetic sensing element 2050, the magnetic sensor 2010 is able to provide both safing and crash detection functions, thereby precluding the need for a separate crash accelerometer. The coils 2042, 2054 and 2062 of the magnetic sensor 2010 could, for example, be constructed of wire wound on an associated bobbin, and then placed over an existing component of the vehicle, for example a hinge 2018 or striker 170.
The coils or sensing elements may incorporate a ferrite or other high permeability magnetic core. Also, highly-tuned coils can be used for magnetic signal generation. Moreover, the width and length of coil bobbins can be adapted to steer the magnetic flux 186. Lastly, the at least one first coil 2042 or the at least one magnetic sensing element 2050 might incorporate ferrite rod coils placed under the vehicle chassis, in the vehicle headliner, in the “A” pillar, or in the “B” pillar, pointing towards the road.
Moreover, the signals associated with the magnetic sensor 2010 can be generated, adapted or processed in a variety of ways, including but not limited to:
-
- 1. Setting up an alternate frequency to create system safing on the rear door 78 to enhance the system safing of the front door 78;
- 2. AM, FM or pulsed demodulation of the magnetic signature;
- 3. Multi-tone, multi-phase electronics;
- 4. A magnetically-biased, phase-shift oscillator for low-cost pure sine wave generation;
- 5. A coherent synthetic or phased-locked carrier hardware- or microprocessor-based system;
- 6. A system of microprocessor gain-or offset-tuning through D/A then A/D self-adjust or self-test algorithm;
- 7. Placing a “standard” in the system safing field for magnetic calibration;
- 8. Inaudible frequencies;
- 9. Microprocessor-generated crystal stabilized frequencies for stability, including microprocessor D/A converter for coherent sine-wave generation;
- 10. Wide-band system electronics;
- 11. Closed loop gain- and phase-control of the signal to a sending-coil (i.e. AGC with the door 78 acting as a delay line), wherein the gain- and phase-control signals are used as sensor outputs;
- 12. AC or DC operation, wherein the DC portion of the signal provides information from the net static magnetic flux 186 of the door 78 in product with the velocity of the impact, but does not provide proximity information, and the AC approach provides the proximity field and allows the system to be ratiometric with the known and stationary transmitter gain;
- 13. In accordance with experiments that have shown that the phase varies as the magnetic gain across the door 78 varies, a phase processor (FM) that has a lower signal-to-noise ratio than a gain processor (AM);
- 14. Monitoring the power delivered by the coil driver, particularly the bypass power, in order to detect impacts near or at the hinge(s) magnetically energized with the at least one first coil;
- 15. A series-resonant coil driver-circuit to increase current to flow to the at least one first coil 2042 so as to improve the signal-to-noise ratio, wherein the associated current to the at least one first coil 2042 is monitored to provide a continuous self-test of the at least one first coil 2042, as well as a measure of the power drawn by the at least one first coil 2042; and
- 16. Using another type of magnetic sensing element 2050, for example a Hall effect or a Giant Magneto-resistive (GMR) device, instead of a second coil 2054.
If both front doors are to be protected, then the effects of temperature and component variation may be mitigated by making a ratiometric measurement of comparable signals from one door 78 relative to another, wherein it is assumed that both doors will not be simultaneously impacted. The ratiometric measurement may also be used to augment the individual measurements from each door 78. Furthermore, a common oscillator may be used to generate a common signal used by each associated first coil 2042, so as to reduce cost and to synchronize the magnetic flux 186 generated at various locations in the vehicle 12.
Whereas the magnetic sensor 2010 has been illustrated herein with the door 78 as a principal sensing element, the magnetic sensor 2010 may generally be adapted to sensing the integrity of any component of any component capable of conducting magnetic flux 186, and would be advantageous for sensing large or long ferromagnetic parts. For example, the magnetic sensor 2010 can be adapted to sensing other body parts, such as fenders, that are attached to the main body of the vehicle by operatively connecting an at least one first coil 2042 between the body part and the main body at the point of attachment.
The proximity or leakage magnetic field comprising the above described second 2088 and third 2094 portions of the magnetic flux 186 can be useful for detecting magnetically permeable objects proximate to a vehicle 12, for example proximate to a door 78 of a vehicle 12; and for detecting the velocity of an object from the affect over time of the object on the permeance of the region proximate to the vehicle 12. This provides for what is termed herein a “radar mode” of operation useful for anticipatory collision sensing, with the following features:
-
- 1. The “radar mode” can be further augmented by the use of independent carrier frequencies. With frequency differentiation on the magnetic “transmitters” the system can determine and differentiate the incoming “magnetically visible” object's “height off of the earth” relative to the upper and lower hinge position. A SUV will send “more signal” to the upper hinge as compared with a low profile sports car.
- 2. The incoming object height information will also support pole versus 214 style-hit scenarios.
- 3. The “radar mode” provides for anticipatory crash sensing, adjacent lane awareness, blind spot awareness, a means for measuring a following distance to a preceding vehicle, a sensor for a collision avoidance system that, for example, could turn the steering wheel as the result of an object detected in the “magnetic fringing field of view” of the automobile door described above, and a sensor for use in a system to automatically center the vehicle between other vehicles in adjacent driving lanes.
- 4. Some quantity of the magnetic flux generated by the hinge coil will enter the space surrounding the automobile door and return from that space and enter the striker coil.
- 5. Permeable objects will be detectable as magnetic “leakage” flux lines from the door enter and exit the near-by-permeable object.
- 6. The list of permeable objects “visible” to the door magnetic fringe field includes, but is not limited to people or relatively large animals, metal objects, automobiles, any object of comparable size to the door and with a distinct permeance, living trees comprising a permeable material.
- 7. The incoming velocity of these objects can be measured.
- 8. A state machine can be used to track object motion history and “anticipate” a collision with an object having sufficient velocity to be a danger to the occupant if the velocity does not change. This pre-crash information is sometimes referred to as information at a “negative time”.
Referring to
For example, the oscillator 2104 may generate either a sinusoidal or square wave signal, which can be either mono-polar or bi-polar, although a mono-polar signal is beneficial in simplifying the associated circuitry of the electrical circuit 2102 and it associated power supply. In one embodiment, the oscillator 2104 is adapted to oscillate at 20 KHz and the associated first resonant circuit 2106 is adapted to have an associated resonant frequency of 10 to 20 KHz. The associated electrical circuit 2102 is adapted to operate at about half the nominal voltage of the associated power supply of the associated electrical circuit 2102, so as to provide for continuous operation over the expected operating cycle of the power supply, e.g. vehicle battery. Accordingly, for a a nominal 12 volt power supply, this oscillator 2104 generates a mono-polar signal of 0-6 volts. Generally, the nominal oscillation frequency of the oscillator 2104 may range between DC (no oscillation) and 100 KHz for a typical vehicle 12, but which may be 1 MHz or higher in a vehicle that has been augmented with supplemental magnetic materials such as mu-metal, ferrite or amorphous metal materials (e.g. METGLAS®). For example, in one set of embodiments, the oscillation frequency of the oscillator 2104 is adapted for the audio to near ultrasonic range of between 5 KHz and 30 KHz. The choice of a particular frequency can be affected by electromagnetic compatibility (EMC) issues associated with the magnetic sensor 2100 in the vehicle 12, for example, so as to avoid interference with other electronic systems in the vehicle, e.g. the AM radio receiver. In one approach, the frequency spectra of the one or more signals responsive to the magnetic flux 186, φ are measured responsive to a crash and analyzed so as to determine an upper bound on the frequencies of relevance to the crash for subsequent processing. Then, the associated oscillation frequency of the oscillator 2104 is adapted to be some factor greater than that upper bound frequency of the measured data, e.g. in accordance with the Nyquist criteria. For example, in one embodiment, the oscillation frequency may be adapted to be a factor of at least two times greater than the maximum frequency of interest, for example, a factor of 2.5. The associated nominal resonant frequency of the first resonant circuit 2106 is adapted to be either the same as or different from the oscillation frequency of the oscillator 2104, depending upon the particular embodiment. The voltage level of the oscillator 2104 and the resistance of the first resonant circuit 2106 are adjusted to provide the level of current through the first coil 2042 (L1) necessary to provide a desired level of magnetic flux 186, φ in the associated magnetic circuit 188. For a given level of current through the first coil 2042 (L1), an increase in the number of turns thereof increases the density of magnetic flux 186, φ thereby increasing the signal-to-noise ratio of the associated response signals.
Referring to
A frequency domain representation of the current through a series combination of an inductor L, capacitor C and resistor R, responsive to a source voltage V(jω) having an oscillatory radian frequency ω is given by:
and the voltage VL across the inductor L is given by:
wherein the resonant frequency ωn and damping ratio ζ are defined respectively as
and ωn and fn are the radian and natural resonant frequencies respectively. For a component of the oscillatory first signal 2044 at the resonant frequency, i.e. at resonance, the inductive and capacitive reactances of the inductor L and capacitor C respectively, i.e. jωL and
respectively, cancel one another, resulting in an impedance Z=R of the series combination. At resonance, current I through the inductor L has a value of I=V/R, and the voltage VL across the inductor L is given by:
Accordingly, referring to
Stated in another way, for a given magnetic flux 186, φ, to be generated in the magnetic circuit 188 by the first coil 2042 (L1) responsive to a first signal 2044, the necessary magnitude of the first signal 2044 is lower for a series resonant condition than for a non-resonant condition. This is beneficial in an automotive environment—wherein the battery voltage is subject to substantial variation during its life cycle, depending upon the state of charge, the load levels, and the operativeness of the associated charging system—by providing for operation using a single-ended nominal 12 volt battery power supply to the electrical circuit 2102 without requiring either an associated voltage magnification circuit or a bi-polar power supply circuit. For example, the series resonant condition provides for operating at a voltage substantially less than the nominal battery voltage—e.g. operating at about 6 volts for a 12 volt nominal battery voltage—so as to provide for uninterrupted sensing during conditions of low battery voltage. This reduces the complexity and cost of the power supply for the associated electrical circuit 2102, and reduces associated power consumption by the components thereof. Operation at or near resonance is also beneficial in improving the electromagnetic compatibility (LMC) of the magnetic sensor 2100 with other systems.
In one embodiment, the resistance R5 of the resistor 2110 (R5) is lower than the resistance RL1 of the first coil 2042 (L1) so as to reduce power consumption by the resistor 2110 (RS) and so as to increase the sensitivity of the current in the first resonant circuit 2106 to changes in the resistance RL1 of the first coil 2042 (L1). At resonance, the inductive reactance of the first coil 2042 (L1) cancels the capacitive reactance of the first capacitor 2108 (CS), so that the component of current in the first resonant circuit 2106 at the resonant frequency is given by the ratio of the source voltage—i.e. the voltage of the first signal 2044 from the oscillator 2104—divided by the total resistance of the first resonant circuit 2106—i.e. the sum of the resistance RL1 of the first coil 2042 (L1), the resistance R5 of the series resistor 2110 (RS), and the resistance of other associated conductors in the first resonant circuit 2106, e.g. coil leads, cables, printed circuitry, and connector(s). The level of the maximum current level at resonance in the first resonant circuit 2106 can be set to a desired level by adjusting either the total series resistance thereof or the magnitude of the first signal 2044, or by adjusting both. The magnitude of the associated magnetic flux 186, φ generated by the first coil 2042 (L1) is proportional to the product of the number of turns N of the first coil 2042 (L1) times the current I therein, wherein the current I is given by the ratio of the level V of the first signal 2044 divided by the total resistance of the first resonant circuit 2106, or
For example, the maximum current I or associated maximum magnetic flux 186, φ may be adjusted to satisfy EMC requirements—e.g. on radiated power—by adjusting either the number of turns N or the total resistance RTotal without impacting the associated operating voltage V of the system, which, for example, may be a mono-polar +6 volts for a nominal 12 volt battery powered system.
The self-capacitance CL1 of the first coil 2042 (L1)—which increases with increasing number of turns N of the first coil 2042 (L1),—in combination with the self-inductance L1′ of the first coil 2042 (L1), provides for inherent low-pass filtering of signals applied to or affecting the first coil 2042 (L1). For example, the first signal 2044 from a square wave oscillator 2104, e.g. a TTL (Transistor Transistor Logic) oscillator, would exhibit harmonics of higher frequency than the fundamental oscillation frequency f0. These harmonics can be attenuated by this effective low-pass filter so as to reduce, or effectively preclude, the generation of components of magnetic flux 186, φ at the harmonic frequencies—which if otherwise generated might cause undesirable electromagnetic signals—thereby improving the electromagnetic compatibility (EMC) of the associated magnetic sensor 2100. Furthermore, increased self-capacitance reduces the electromagnetic susceptibility of the magnetic sensor 2100 to external interference.
In accordance with a first embodiment of the magnetic sensor 2100.1—in what is referred to as a transformer mode of operation—the magnetic flux 186, φ generated in the magnetic circuit 188 by the first coil 2042 located at a first location 2048 on the magnetic circuit 188, responsive to the first signal 2044 applied thereto, is sensed by a magnetic sensing element 2050, e.g. a second coil 2054 (L2), at a second location 2052 on the magnetic circuit 188, which generates a second signal 2114 responsive to the reluctance of the magnetic circuit 188, for example, responsive to a crash affecting at least one element of the magnetic circuit 188, or responsive to a magnetic-flux-influencing object proximate to a proximity flux component 2088 of the magnetic flux 186 of the magnetic circuit 188. The magnetic sensor 2100.1 can be adapted so as to provide for sensing either the magnitude of the second signal 2114 or components thereof, e.g. DC or AC, or for sensing the phase of the second signal 2114 in relation to that of the associated first signal 2044. For example, in one embodiment that operates at a relatively low frequency, the relative phase between the first 2044 and second 2114 signals might be used as a the primary measure to detect a crash.
Referring to
Referring to
The capacitance of the second capacitor 2118 (CP) and the inductance L2′ of the second coil 2054 (L2) are adapted, for example, to set the second resonant frequency fn
The parallel combination of the second coil 2054 (L2) and the second capacitor 2118 (CP) is beneficial for improving electromagnetic compatibility (EMC) by reducing susceptibility to externally generated electromagnetic fields, wherein at the associated relatively high frequencies, the impedance of the second capacitor 2118 (CP) is relatively low, thereby limiting the associated signal levels that can be generated thereacross. Accordingly, the second resonant circuit 2116 provides for enhancing or maximizing the level of the second signal 2114 for signals of interest, and for attenuating undesirable signals associated with electromagnetic noise.
It should be understood that the first and second embodiments of the magnetic sensor 2100 can be practiced either jointly in combination with one another, as illustrated in
In accordance with a third embodiment of the magnetic sensor 2100.3, the electrical circuit 2102 associated with the first coil 2042 (L1) is adapted to sense one or more variables associated with the first resonant circuit 2106, for example, the voltage across the first coil 2042 (L1), the current through the first coil 2042 (L1) as measured by the voltage across the resistor 2110 (RS) in series with the first coil 2042 (L1), or the voltage across the first capacitor 2108 (CS); so as to provide for determining therefrom a measure responsive to the inductance or resistance of the first coil 2042 (L1), for example, the inductance L1′ of the first coil 2042 (L1), the magnitude of the voltage across the first coil 2042 (L1), the magnitude of the current through the first coil 2042 (L1), the phase angle between the voltage across the first coil 2042 (L1) and the current through the first coil 2042 (L1), the reactive power applied to the first coil 2042 (L1), or the real power that is absorbed by the first coil 2042 (L1). The measure responsive to the inductance or resistance of the first coil 2042 (L1) may then be used to either diagnose the operativeness of the first resonant circuit 2106—particularly the first coil 2042 (L1)—or to detect the occurrence of a crash in accordance with a self-inductance mode of operation—particularly impacts proximate to the first location 2048, (e.g. the hinge 2018 side of the door 78) of the first coil 2042 (L1),—for example, in accordance with the teachings of U.S. application Ser. No. 09/648,606 filed on Aug. 26, 2000, now U.S. Pat. No. 6,587,048, which is incorporated herein by reference. For example, the current in the first coil 2042 (L1) can be sensed and compared with one or more thresholds to determine if the first resonant circuit 2106 is operating normally for a nominal condition of the vehicle 12, or, for example, if one or more turns of the first coil 2042 (L1) are shorted. An impact to the vehicle 12 affecting the magnetic circuit 188 would modulate the voltage across, the current through, or the inductance of the first coil 2042 (L1) to which the above-identified measures are responsive. The measure responsive to the inductance or resistance of the first coil 2042 (L1) can be detected and sensed in real time so as to provide for real time detection of the operativeness of the first resonant circuit 2106, e.g. so as to determine whether or not the first coil 2042 (L1) is generating a magnetic flux 186, φ in the magnetic circuit 188. Furthermore, different magnetic sensors 2100 at different locations in the vehicle 12, e.g. the A-pillar, B-pillar or C-pillar of the vehicle 12 may be adapted to verify the operativeness of one another, and thereby provide for mutual safing of different magnetic sensors 2100.
The current I in the first coil 2042 (L1) generates a magnetic flux 186, φ in the associated magnetic circuit 188. This magnetic flux 186, φ stores an associated energy therein which is in balance with both the energy transferred thereto by the first coil 2042 (L1), and with associated energy losses, e.g. resulting from either eddy currents, hysteresis or radiation. A mechanical perturbation of one or more elements of the magnetic circuit 188, e.g. the door 78, affects this energy balance, resulting in a corresponding affect on the current I received or absorbed by the first coil 2042 (L1), and it is believed that the magnitude of this affect is related to the mechanical energy associated with the associated mechanical perturbation.
Stated in another way, the inductance L1′ of the first coil 2042 (L1) is responsive to the associated coil geometry (including wire size, number of turns, and turn shape and radii) and to the reluctance of the associated magnetic circuit 188. Accordingly, a change to either the magnetic circuit 188, or the to coil geometry,—e.g. responsive to a crash—will cause an associated change in the associated inductance L1′ of the first coil 2042 (L1), which in turn causes an associated change in the impedance ZL thereof responsive to an oscillatory signal from the oscillator 2104, which in turn causes an associated change in the impedance Z of the first resonant circuit 2106 to which the first signal 2044 from the oscillator 2104 is applied. Accordingly, for a first signal 2044 having a constant amplitude V, the resulting current I through the first coil 2042 (L1) given as I=V/Z will vary responsive to the value of Z, with is responsive to and indicative of the mechanical perturbation of either the associated magnetic circuit 188 or the first coil 2042 (L1).
Furthermore, certain types of crashes, e.g. pole impacts, the extent to which a crash induced perturbation of the magnetic circuit 188 influences the resulting current I in the first coil 2042 (L1) is responsive to the proximity of the crash location to the first coil 2042 (L1). Accordingly, in accordance with one embodiment, the magnitude of the variation in current I in the first coil 2042 (L1) can be used as a measure of the proximity of the crash to the first coil 2042 (L1). In accordance with another embodiment, the variation in current I in the first coil 2042 (L1) in relation to the variation in the associated signal from one or more associated magnetic sensing elements 2050 can be used to determine the location of the crash in relation to the locations of the first coil 2042 (L1) and the one or more associated magnetic sensing elements 2050. Generally, the modulation of the current I in the first coil 2042 (L1) is useful for sensing crash severity and location, and for verifying the operativeness of the first coil 2042 (L1). By relatively increasing or maximizing the current I in the first coil 2042 (L1) using a first resonant circuit 2106 as described hereinabove, the associated detection sensitivity is relatively increased or maximized.
Referring to
It should be understood, that the analog-to-digital converters 2130, 2138, 2142 and 2148 would cooperate with associated low pass anti-aliasing filters either incorporated therein, or incorporated in other signal conditioning elements that preprocess the signal(s) thereto, so as to prevent high frequency information from aliasing as corresponding lower frequency information in the sampled signals. For example, in accordance with the Nyquist sampling criteria, the sampling frequency of the analog-to-digital converters 2130, 2138, 2142 and 2148 would be at least twice as great as the cut-off frequency of the associated anti-aliasing filter. It is beneficial to adapt the anti-aliasing filter, for example, by using a single pole anti-aliasing filter, so as to provide for avoiding excessive phase shift or delay in the filtered signal, so as to provide for an associated relatively fast step response.
The second 2144 and third 2150 demodulators, if present, provide for detecting one or more of a magnitude, a phase, a relative phase, in in-phase component or a quadrature-phase component of the respective input signals to the respective demodulators 2144, 2150. More particularly, each respective input signal comprises a carrier at the oscillation frequency f0, which carrier is modulated by a respective modulation signal, and the demodulators 2144, 2150, if present, provide for generating one or measures of amplitude or phase—including in-phase and quadrature-phase signal components—responsive to associated characteristics of the respective modulation signal. Depending upon their configuration, the second 2144 and third 2150 demodulators, if present, may be connected either directly to the processor 2132, e.g. to one or more digital inputs, or through associated third 2142 and fourth 2148 analog-to-digital converters. Furthermore, the functions of the second 2144 and third 2150 demodulators could be combined in a single demodulator that generates either analog or digital output signals, or both, and is which appropriately connected to the processor 2132. Yet further, one or more demodulation functions could also be carried out directly by the processor 2132 on one or more of the respective input signals. Yet further, one or all of the demodulators 2126, 2144 or 2150 (e.g. the second demodulator 2144 as illustrated in
The voltage VRS across the resistor 2110 (RS) provides a measure of the current I therethrough, given by I=VRS/RS, which is also a measure of the current through the first coil 2042 (L1) in series therewith. The measure of current I will be responsive to the total resistance RTotal of the first resonant circuit 2106 and to the sum of the inductive and capacitive reactances of the first coil 2042 (L1) and the first capacitor 2108 (CS) respectively, the latter of which sum to zero at resonance. Increasing the gain of the fourth amplifier 2146 increases the sensitivity of the measure of current I to the resistance RL1 of the first coil 2042 (L1), and accordingly, the sensitivity to detecting whether one or more turns thereof are shorted. A shorting of one or more coils of the first coil 2042 (L1) causes the associated current I to increase. Furthermore, if one or more turns of the first coil 2042 (L1) are shorted, then the self-inductance L1′ of the first coil 2042 (L1) would also be affected, e.g. reduced, which would in turn affect the current I and the associated measure thereof, and the total reactance of the first resonant circuit 2106 would become increasingly capacitive reactive, thereby affecting the phase of the current I through the resistor 2110 (RS) relative to the voltage of the first signal 2044 applied by the oscillator 2104. The self-inductance L1′ of the first coil 2042 (L1) is also responsive to the reluctance of the associated magnetic circuit 188, changes to which—e.g. responsive to a crash or a proximate object—also affect the current I and the associated measure thereof. It is expected that the sensitivity of the self-inductance L1′ of the first coil 2042 (L1) to changes in the reluctance of the associated magnetic circuit 188 can be increased by increasing the number of turns of the first coil 2042 (L1). Additional fourth amplifiers 2146 and associated electronics may be added to provide for a plurality of current responsive signals, each having a different level of associated amplifier gain and resulting sensitivity. For example, a different sensitivity might be used for detecting changes of resistance RL1—e.g. caused by shorted turn condition—of the first coil 2042 (L1) than might be used for detecting crash-induced changes to the inductance L1′ thereof. Alternatively, a single gain-controllable fourth amplifier 2146 could be used, with the gain thereof controlled by the processor 2132.
For a pure inductor L, the relationship between the voltage VL across to the current IL through the inductor L is given by:
Accordingly, for an ideal inductor, the current I therethrough lags the voltage VL thereacross by 90 degrees, and in the frequency domain, the inductance is given by:
Alternatively, in the time domain:
However, for a real inductor, e.g. first coil 2042 (L1) represented by a the second-order system illustrated in
The processor 2132 senses the voltage VL and current I signals in real time in order to either diagnose a failure of or change to either the first coil 2042 (L1) or elements of the associated first resonant circuit 2106, or to discriminate a crash or other condition affecting the magnetic circuit 188. In addition to using the magnitudes of the voltage VL and current I, the processor can also use the relative phase thereof, or the phase of either the voltage VL of current I relative to that of the first signal 2044, in order to determine, for example, the inductance L1′ or impedance of the first coil 2042 (L1), the resistance RL1 thereof, or the resistance of the first resonant circuit 2106.
The processor 2132 may further determine the power applied to the first coil 2042 (L1)—either reactive (V*I), real (V*I*cos(θ)), or both—which can be used as addition information for either failure detection, crash sensing, or sensing some other measure responsive to the reluctance of the magnetic circuit 188.
The quality factor, or Q, of the first resonant circuit 2106 is related to the bandwidth of the magnetic sensor 2100, and is affected by the resistance of the first resonant circuit 2106—i.e. either the intrinsic resistance of the coil, the resistance of the associated series resistor 2110 (RS), or the equivalent series resistance (ESR) of the associated first capacitor 2108 (CS). Accordingly, the Q of the first resonant circuit 2106 can be set or adjusted by setting or adjusting the associated resistance of the first resonant circuit 2106, for example, either by adjusting the intrinsic resistance of the first coil 2042 (L1)—which is described more fully hereinbelow,—or by adjusting the resistance of the series resistor 2110 (RS). The overall sensitivity of the magnetic sensor 2100 to associated magnetic disturbances in or to the magnetic circuit 188 is affected by the relative amount by which the oscillation frequency differs from the resonant frequency of the first resonant circuit 2106, and this sensitivity to that change is affected by the Q of the first resonant circuit 2106. For example, this sensitivity or gain is highest when the oscillation frequency is equal to the resonant frequency, and is reduced as the relative difference increases, as illustrated in
In accordance with a second embodiment of a subsystem for sensing one or more variables associated with the first resonant circuit 2106, the voltage VL across the first coil 2042 (L1) is sensed as described hereinabove, without separately sensing the voltage VRS across the resistor 2110 (RS). The voltage VL across the first coil 2042 (L1) will be responsive to the current I through the first coil 2042 (L1) as follows:
VL=I·ZL (10)
where ZL is the impedance of the first coil 2042 (L1). The current I through the first resonant circuit 2106 is given by:
where V is the voltage of the first signal 2044, ZCS is the impedance of the first capacitor 2108 (CS), and RS is the impedance of the resistor 2110 (RS) (if present). The impedance ZL of the first coil 2042 (L1) is then given as a function of the voltages V of the first signal 2044 and VL across the first coil 2042 (L1) as follows:
For example, assuming that the voltage V of the first signal 2044, the impedance ZC the first capacitor 2108 (CS), and the impedance RS of the resistor 2110 (RS) (if present) are constant, then the impedance ZL of the first coil 2042 (L1) is given as a function of the voltage VL thereacross.
In accordance with a third embodiment of a subsystem for sensing one or more variables associated with the first resonant circuit 2106, the voltage VRS across the resistor 2110 (RS) is sensed as described hereinabove, without separately sensing the voltage VL across the first coil 2042 (L1). The voltage VRS across the resistor 2110 (RS) is responsive to the current IL through the first coil 2042 (L1) as described hereinabove, and is responsive to the condition of resonance as illustrated in
In accordance with a fourth embodiment of a subsystem for sensing one or more variables associated with the first resonant circuit 2106, the voltage VC across the first capacitor 2108 (CS)—or the voltage (VC+VRS) across the series combination of the first capacitor 2108 (CS) and resistor 2110 (RS)—can be sensed as an alternative to, or in addition to, sensing the voltage VL across the first coil 2042 (L1) or the voltage VRS across the resistor 2110 (RS). For example, the voltage VL across the first coil 2042 (L1) is given by:
VL=V1−(VCS+VRS) (13)
Referring to
Referring to
Referring to
This distribution of capacitance to both sides of the first coil 2042 (L1) is beneficial in providing for tolerating shorts to either power or ground in the conductors that couple the first coil 2042 (L1) to the associated electrical circuit 2102, which shorts might otherwise damage the associated electrical circuit 2102, but which instead are readily detected by the above described embodiments for sensing one or more variables associated with the first resonant circuit 2106. For example, typically the first coil 2042 (L1) would be connected to the associated electrical circuit 2102 with a cable or wiring harness, which might be susceptible to the above described faults during assembly or operation of the vehicle 12. The resonance conditions of the first resonant circuit 2106 are otherwise as described hereinabove for a first resonant circuit 2106 incorporating a single first capacitor 2108 (CS).
In accordance with a fifth embodiment of the magnetic sensor 2100.5, the resistance RL1 of the first coil 2042 (L1) increases if the wire gauge thereof is reduced, or the number of turns N thereof is increased. If the resistance RL1 of the first coil 2042 (L1) is sufficient to limit the maximum current I in the first resonant circuit 2106 to an acceptable level, then the resistor 2110 (RS) can be eliminated from the first resonant circuit 2106. This arrangement also provides for improved sensitivity of the voltage (VL) across the first coil 2042 (L1) to changes in the resistance RL1 of the first coil 2042 (L1), e.g. as might be caused by a shorting of one or more turns within the first coil 2042 (L1); which otherwise for a system incorporating a resistor 2110 (RS) in the first resonant circuit 2106, increases as the ratio of the resistance RL1 to the resistance RS increases. For example, the intrinsic resistance of the first coil 2042 (L1) can be set to a value between about 0.1 ohms and 10 ohms by adjusting the associated wire size (gauge) and/or length of wire (number of turns). For a first coil 2042 (L1) of 60 turns, if the total intrinsic resistance thereof were 0.1 ohms, the resistance per turn would be 0.0001666 ohms per turn; whereas if the total intrinsic resistance were 10 ohms, the resistance per turn would be 0.16 ohms per turn, the latter of which would be substantially easier to measure. In addition to being affected by the total intrinsic resistance of the first coil 2042 (L1), the detectability of shorted turns is also affected by resistance of the series resistor 2110 (RS) in relation to that of the first coil 2042 (L1), and can be improved by increasing the gain of the fourth amplifier 2146 used to amplify the voltage across the resistor 2110 (RS).
In accordance with the above described embodiments, the oscillation frequency f0 may be adapted to provide for a resonant or near-resonant condition at the nominal state of the vehicle 12 and the associated magnetic circuit 188 (i.e. pre-crash); or may be adapted to be off-resonance for the nominal condition of the vehicle body 168 and the associated magnetic circuit 188, and then to provide for a resonant or near-resonant condition responsive to a crash, as a result of an associated shift in the inductance L1′ or L2′ of the first coil 2042 (L1) or the second coil 2054 (L2). Furthermore, the magnetic sensor 2100 could incorporate a plurality of distinct frequencies, different frequencies being adapted to provide for an associated resonance for different associated conditions of the vehicle body 168.
Referring to
The particular operating point on the frequency response characteristic—e.g. as illustrated in FIG. 110—of the first resonant circuit 2106 will affect the amount of power transferred to the magnetic circuit 188 by the oscillator 2104/first buffer amplifier 2112. In one embodiment, upon initialization of the magnetic sensor 2100, the resonant frequency of the first resonant circuit 2106 and the nature of the associated frequency response is identified by sweeping the oscillation frequency and monitoring the response from the associated magnetic sensing element 2050, generally as described hereinabove, either using the primary oscillator 2104 as the signal source, or another oscillator, so as to provide for measuring both the resonant frequency of the first resonant circuit 2106, and its associated frequency response. If the resulting measured resonant frequency is different from the nominal oscillation frequency f0 of the oscillator 2104, then thereafter, when operating at the nominal oscillation frequency f0, one or more software or hardware parameters or variables would be adjusted, e.g. in accordance with a correction factor, to accommodate the associated degradation in gain caused by operating with an oscillation frequency f0 that differs from the resonant frequency of the associated first resonant circuit 2106. Accordingly, this embodiment provides for adapting to relatively long term changes in the magnetic sensor 2100, for example, as might result from either production variability, temperature, or aging. A warning can be generated or activated, e.g. via an indicator or alarm, if the magnitude of the associated correction factor exceeds a threshold, e.g. indicative of the need for maintenance or repair.
For example, if the first coil 2042 (L1) were an ideal inductor having an inductance of L1, then if the resonant frequency were determined to be fn, then the inductance L1 would be given by:
In accordance with another aspect of the sixth embodiment, either the oscillator 2104 or an associated amplifier, e.g. the first buffer amplifier 2112, may be controlled responsive to a signal 2174 from the processor 2132, or another controller, so as to control the level of current I to the first coil 2042 (L1), as sensed from the voltage VRS across the resistor 2110 (RS). By operating at least near resonance, the impedance of the first resonant circuit 2106 is at least substantially resistive, which simplifies the associated control algorithm for controlling the level of current I. For example, the current I may be controlled to a constant value using a relatively low bandwidth control algorithm which is fast enough so as to correct for long term variations, e.g. resulting from production variations, temperature effects, or aging, but is slow enough so as to not adversely affect a crash induced perturbation or variation of the current I. Accordingly, this closed loop current control system provides for maintaining the nominal level of current I through the first coil 2042 (L1) so as to correspondingly maintain an associated nominal level of magnetic flux 186, φ in the associated magnetic circuit 188, thereby accommodating changes to the first resonant circuit 2106 that might affect the resonant frequency thereof, and accordingly, might otherwise adversely affect the level of current I as a result of the inherent frequency response of the first resonant circuit 2106 and its associated bandwidth.
Responsive to the detection of a crash, or other condition affecting the vehicle body 168 or associated magnetic circuit 188, or responsive to the detection of a failure of a component of the magnetic sensor 2100, by any of the above described embodiments, the processor 2132 can then either actuate an associated safety restraint actuator 110, or an associated indicator 2178, as necessary to either protect or inform an occupant of the vehicle 12.
Referring to
Referring to
The first magnetic sensor 2202 comprises an associated oscillator 2210.1 operatively coupled to an associated coil driver 2212.1 which is operatively coupled to an associated first resonant circuit 2214.1 comprising an associated first coil 2216.1 in series with an associated first capacitor 2218.1, wherein the associated first coil 2216.1 is located at an associated first location 2220.1 on an associated magnetic circuit 2222.1 thereof. The first magnetic sensor 2202 further comprises an associated magnetic sensing element 2224.1 comprising, for example, an associated second coil 2224.1′, which is illustrated as part of a second resonant circuit 2226.1 further comprising a second capacitor 2228.1 in parallel with the second coil 2224.1′. The associated magnetic sensing element 2224.1 is located at an associated second location 2230.1 on the associated magnetic circuit 2222.1. For example, the first 2220.1 and second 2230.1 locations respectively are illustrated as respectively comprising a hinge 2018 and a striker 170 of a door 78 on the left side 2206 of the vehicle 12. The output of the second resonant circuit 2226.1 is amplified/buffered by an associated first amplifier 2232.1, e.g. a differential amplifier, the output of which is processed by an associated preprocessing circuit 2234.1, for example, comprising elements comparable to the first amplifier 2122, first coupling capacitor 2124, first demodulator 2126, second coupling capacitor 2134, second amplifier 2128, and third amplifier 2136 as illustrated in
The second magnetic sensor 2204 comprises an associated oscillator 2210.2 operatively coupled to an associated coil driver 2212.2 which is operatively coupled to an associated first resonant circuit 2214.2 comprising an associated first coil 2216.2 in series with an associated first capacitor 2218.2, wherein the associated first coil 2216.2 is located at an associated first location 2220.2 on an associated magnetic circuit 2222.2 thereof. The second magnetic sensor 2204 further comprises an associated magnetic sensing element 2224.2 comprising, for example, an associated second coil 2224.2′, which is illustrated as part of a second resonant circuit 2226.2 further comprising a second capacitor 2228.2 in parallel with the second coil 2224.2′. The associated magnetic sensing element 2224.2 is located at an associated second location 2230.2 on the associated magnetic circuit 2222.2. For example, the first 2220.2 and second 2230.2 locations respectively are illustrated as respectively comprising a hinge 2018 and a striker 170 of a door 78 on the right side 2208 of the vehicle 12. The output of the second resonant circuit 2226.2 is amplified/buffered by an associated first amplifier 2232.2, e.g. a differential amplifier, the output of which is processed by an associated preprocessing circuit 2234.2, for example, comprising elements comparable to the first amplifier 2122, first coupling capacitor 2124, first demodulator 2126, second coupling capacitor 2134, second amplifier 2128, and third amplifier 2136 as illustrated in
The first 2202 and second 2204 magnetic sensors, as described heretofore, are adapted to each individually function in cooperation with the corresponding left 2206 and right 2208 sides of the vehicle 12 in accordance with any of the earlier described embodiments of magnetic sensors, for example, as identified by magnetic sensors 2010, 2100, 2100.1, 2100.2, 2100.3, 2100.4, 2100.5, 2100.6.
Furthermore, the oscillation frequency f1 of the oscillator 2210.1 associated with the first magnetic sensor 2202 is adapted to be different from the oscillation frequency f2 associated with the oscillator 2210.2 of the second magnetic sensor 2204, so that the signals from the corresponding first coils 2216.1 and 2216.2 can be differentiated from one another, to the extent that the magnetic circuits 2222.1, 2222.2 associated with the first coils 2216.1, 2216.2 associated with one magnetic sensor 2202, 2204 interact with the magnetic sensing elements 2224.2, 2224.1 associated with the other magnetic sensor 2204, 2202. For example, in one embodiment, the oscillation frequency f1 of the oscillator 2210.1 associated with the first magnetic sensor 2202 is about 10 KHz, whereas the oscillation frequency f2 associated with the oscillator 2210.2 of the second magnetic sensor 2204 is about 20 KHz. It may be beneficial for the respective oscillation frequencies f1 and f2 to be adapted so that one is not a harmonic of the other, for example, so that the oscillation frequencies f1 and f2 are relatively indivisible or irrational with respect to one another, so as to preclude the prospect of a harmonic of a signal generated by one magnetic sensor 2202, 2204 being interpreted as originating from the other magnetic sensor 2204, 2202.
The first magnetic sensor 2202 further comprises an associated third resonant circuit 2240.1, e.g. comprising a series combination of an associated inductor 2242.1 (e.g. a third coil 2242.1′) and a third capacitor 2244.1. The third resonant circuit 2240.1 further comprises an associated current sensor 2246.1, for example an associated series resistor 2248.1 and an associated second amplifier 2250.1, e.g. a differential amplifier, adapted to measure the voltage across the associated series resistor 2248.1. The current sensor 2246.1 may be embodied in other ways, for example by measuring the voltage across either the associated inductor 2242.1 or the associated third capacitor 2244.1, or by measuring a magnetic field generated by the current flowing in the associated third resonant circuit 2240.1. The third resonant circuit 2240.1 is adapted to have a resonant frequency f3.1 that is substantially equal to the oscillation frequency f2 associated with the oscillator 2210.2 of the second magnetic sensor 2204. The output of the associated current sensor 2246.1, e.g. the output of the associated second amplifier 2250.1, is operatively coupled to a second analog-to-digital converter 2252.1, and the output therefrom is operatively coupled to the processor 2238.
Furthermore, the second magnetic sensor 2204 further comprises an associated third resonant circuit 2240.2, e.g. comprising a series combination of an associated inductor 2242.2 (e.g. a third coil 2242.2′) and a third capacitor 2244.2. The third resonant circuit 2240.2 further comprises an associated current sensor 2246.2, for example an associated series resistor 2248.2 and an associated second amplifier 2250.2, e.g. a differential amplifier, adapted to measure the voltage across the associated series resistor 2248.2. The current sensor 2246.2 may be embodied in other ways, for example by measuring the voltage across either the associated inductor 2242.2 or the associated third capacitor 2244.2, or by measuring a magnetic field generated by the current flowing in the associated third resonant circuit 2240.2. The third resonant circuit 2240.2 is adapted to have a resonant frequency f3.2 that is substantially equal to the oscillation frequency f1 associated with the oscillator 2210.1 of the first magnetic sensor 2202. The output of the associated current sensor 2246.2, e.g. the output of the associated second amplifier 2250.2, is operatively coupled to a second analog-to-digital converter 2252.2, and the output therefrom is operatively coupled to the processor 2238.
The magnetic circuit 2222.1 associated with the first coil 2216.1 of the first magnetic sensor 2202 includes both second locations 2230.1 and 2230.2 respectively associated with the first 2202 and second 2204 magnetic sensors respectively. Similarly, the magnetic circuit 2222.2 associated with the first coil 2216.2 of the second magnetic sensor 2204 includes both second locations 2230.2 and 2230.1 respectively associated with the second 2204 and first 2202 magnetic sensors respectively. Accordingly, magnetic flux 186, (generated by the first coil 2216.1 of the first magnetic sensor 2202 is sensed by the magnetic sensing element 2224.2 of the second magnetic sensor 2204, and magnetic flux 186, (generated by the first coil 2216.2 of the second magnetic sensor 2204 is sensed by the magnetic sensing element 2224.1 of the first magnetic sensor 2202. The third resonant circuits 2240.1, 2240.2 are series resonant, and accordingly, have a minimum resistance at their respective resonant frequencies f3.1, f3.2, so that the frequency response of current therethrough exhibits a maximum a the respective resonant frequencies f3.1, f3.2. Stated in another way, each third resonant circuit 2240.1, 2240.2 acts as a current sink at its respective resonant frequency f3.1, f3.2, and a measure of current therethrough provides a measure of the magnitude of an associated frequency component of the magnetic flux 186, φ, having the corresponding resonant frequency f3.1, f3.2, that is sensed by the corresponding first coil 2216.1, 2216.2. Accordingly, the current sensed by the current sensor 2246.1 associated with the first magnetic sensor 2202 provides a measure of the operativeness and operation of the first coil 2216.2 associated with the second magnetic sensor 2204, and the current sensed by the current sensor 2246.2 associated with the second magnetic sensor 2204 provides a measure of the operativeness and operation of the first coil 2216.1 associated with the first magnetic sensor 2202, so that each magnetic sensor 2202, 2204 can be used to verify the operation of the other, and thereby provide a measure for safing the other magnetic sensor 2204, 2202.
Responsive to a first measure of operativeness of the first coil 2216.1 associated with the left side 2206 of the vehicle 12—which first measure of operativeness is responsive a signal from the current sensor 2246.2 associated with the third resonant circuit 2240.2 associated with the second magnetic sensor 2204 associated with the right side 2208 of the vehicle 12—the processor 2238 provides for disabling a first safety restraint actuator 2254.1 associated with the left side 2206 of the vehicle 12 if the first measure of operativeness indicates that the first coil 2216.1 is inoperative. Otherwise, if the first magnetic sensor 2202 is otherwise operative, then the first safety restraint actuator 2254.1 associated with the left side 2206 of the vehicle 12 is actuated responsive to a signal from the associated magnetic sensing element 2224.1 associated with the first magnetic sensor 2202 associated with the left side 2206 of the vehicle 12.
Responsive to a second measure of operativeness of the first coil 2216.2 associated with the right side 2208 of the vehicle 12—which second measure of operativeness is responsive a signal from the current sensor 2246.1 associated with the third resonant circuit 2240.1 associated with the first magnetic sensor 2202 associated with the left side 2206 of the vehicle 12—the processor 2238 provides for disabling a second safety restraint actuator 2254.2 associated with the right side 2208 of the vehicle 12 if the second measure of operativeness indicates that the first coil 2216.2 is inoperative. Otherwise, if the second magnetic sensor 2204 is otherwise operative, then the second safety restraint actuator 2254.2 associated with the right side 2208 of the vehicle 12 is actuated responsive to a signal from the associated magnetic sensing element 2224.2 associated with the second magnetic sensor 2204 associated with the right side 2208 of the vehicle 12.
Referring again to
For example, referring to
|Z|=√{square root over (XZ2+R2)} (16)
and the phase angle θ of which from the abscissa is given by:
where XZ is the net reactance of the series LC circuit 2300.1—positive for net inductance, negative for net capacitance,—and R is the resistance of the series LC circuit 2300.1, i.e. the resistance RL of the first coil 2042 (L1).
In the table of
Similarly, in the fourth embodiment of the magnetic sensor 2100.4 illustrated in
In a practical magnetic sensor 2100 incorporating a series LC circuit 2300, the associated first coil 2042 (L1) is subject to tolerance, i.e. part-to-part variation, and variation in the inductance L, thereof over time, or responsive to operating conditions. Furthermore, the associated capacitance(s) C of the first capacitor 2108 (CS), or the third 2170 (C1) and fourth 2172 (C2) capacitors, may be practically limited to a specific set of available values, i.e. those which are available in production parts. Yet further, there may be a preferred inductance L1 of the first coil 2042 (L1) so as to provide for cooperation of the first coil 2042 (L1) with the associated magnetic circuit 188 to be sensed.
Referring to
The first coil 2042 (L1) is located so as to be magnetically coupled to the associated magnetic circuit 188 to be sensed by the magnetic sensor 2100.7. In one set of embodiments, the first capacitor 2170 (C1) and second inductor 2316 (L2) are located in the associated electrical circuit 2102 of the magnetic sensor 2100.7, for example, in the circuitry of an associated electronic module, for example, to which the first coil 2042 (L1) might be coupled with an associated cable of a wiring harness. Alternatively, one or both of the first capacitor 2170 (C1) and second inductor 2316 (L2) could be co-located with the first coil 2042 (L1), or could be separately located.
The third embodiment of the series LC circuit 2300.3 also provides for reducing the necessary capacitance of the associated first capacitor 2170 (C1) for a given nominal impedance characteristic of the series LC circuit 2300.3. For example, this can be seen for a magnetic sensor 2100.7 with a nominal impedance characteristic that is a resonance condition, wherein the associated resonant frequency ω is given by ω=1/√(LC), and for a given resonant frequency c, as the total inductance L is increased, for example, by adding the second inductor 2316 (L2) in series with the first coil 2042 (L1), then the associated capacitance C would be decreased in order to maintain the given resonant frequency ω. Accordingly, the third embodiment of a series LC circuit 2300.3 provides for independently selecting the capacitance value of the first capacitor 2170 (C1) and the inductance L, of the first coil 2042 (L1) so as to possibly reduce the cost of the associated magnetic sensor 2100.7 for a given level of sensing performance. For example, relatively smaller commercial production capacitors may be relatively cheaper, or exhibit relatively less variability, than relatively larger commercial production capacitors, all else being equal.
Referring to
For example, referring to
Furthermore, referring to
Accordingly, in accordance with the second aspect of the impedance adaptation circuit 2314.2, as embodied in the eighth embodiment of a magnetic sensor 2100.8, the fixed or adjustable capacitance 2318 (CX) and the fixed or adjustable inductance 2320 (LX), either individually alone, or in combination with one another, may be used to adjust the nominal impedance of the associated fourth embodiment of the series LC circuit 2300.4, so as to either compensate for variation in the associated inductance L1 of the first coil 2042 (L1), or to provide for determining the inductance L1 of the first coil 2042 (L1).
For example, the inductance L, of the first coil 2042 (L1) would typically be subject to part-to-part variability, and possibly variability over time. For operation of a series LC circuit 2300.4 with a nominal resonant impedance characteristic, the capacitance CX of the adjustable capacitance 2318 (CX), and/or the inductance LX of the adjustable inductance 320 (LX) may be adjusted under nominal conditions so as to substantially cancel the inductive reactance XL1 of the first coil 2042 (L1), so as to provide for a substantially resonant series LC circuit 2300.4. The particular values of the adjustable capacitance 2318 (CX), and/or the inductance LX of the adjustable inductance 2320 (LX) will depend upon the particular inductance L1 of the first coil 2042 (L1) at the time of compensation, which, for example, might be done when the vehicle 12 is first activated, i.e. at a “key-on” condition, so as to provide for compensating for both part-to-part variability, and variability of a given part over time. As with the seventh embodiment of the magnetic sensor 2100.7, the adjustable inductance 2320 (LX) of the eighth embodiment of a magnetic sensor 2100.8 provides for utilizing relatively smaller, relatively less expensive or relatively less variable, capacitors C*, C1-CN in the associated fixed or adjustable capacitance 2318 (CX). Generally, the second aspect of the impedance adaptation circuit 2314.2, as embodied in the eighth embodiment of a magnetic sensor 2100.8, provides for using relatively wider tolerance (e.g. 20% tolerance instead of 1% tolerance), lower cost parts, in the associated electronic circuitry.
As another example, the second aspect of the impedance adaptation circuit 2314.2, as embodied in the eighth embodiment of a magnetic sensor 2100.8, may be used to determine the inductance L1 of the first coil 2042 (L1), for example, by adjusting either or both the capacitance CX of the adjustable capacitance 2318 (CX), and/or the inductance LX of the adjustable inductance 2320 (LX), until a particular impedance condition—for example, a resonant condition—is achieved, wherein the then known values of the capacitance CX of the adjustable capacitance 2318 (CX), and/or the inductance LX of the adjustable inductance 2320 (LX), in combination with the known operating frequency ω, can then be used to determine a measure of the inductance L1 of the first coil 2042 (L1). In this application, the relative precision of the associated capacitors C*, C1-CN and inductors L*, L1-LM, and the relative precision of the frequency ω setting, would then determine the relative accuracy of the associated resulting measure of the inductance L1 of the first coil 2042 (L1). Alternatively, instead of determining the inductance L1 of the first coil 2042 (L1) per se, the particular capacitance CX of the adjustable capacitance 2318 (CX), and/or the inductance LX of the adjustable inductance 2320 (LX) could be used to establish a threshold for detecting changes to the inductance L1 of the first coil 2042 (L1), for example, for purposes of establishing a detection threshold for use in detecting a crash or in controlling the actuation of a safety restraint actuator 110 responsive thereto.
As with the seventh embodiment of the magnetic sensor 2100.7, in the eighth embodiment of a magnetic sensor 2100.8, the first coil 2042 (L1) is located so as to be magnetically coupled to the associated magnetic circuit 188 to be sensed by the magnetic sensor 2100.7. In one set of embodiments, the capacitors C*, C1-CN and inductors L*, L1-LM are located in the associated electrical circuit 2102 of the magnetic sensor 2100.8, for example, in the circuitry of an associated electronic module, for example, to which the first coil 2042 (L1) might be coupled with an associated cable of a wiring harness. Alternatively, some or all of the capacitors C*, C1-CN and inductors L*, L1-LM could be co-located with the first coil 2042 (L1), or could be separately located.
It should be understood that the above described embodiments, although described separately herein, can be combined with one another as additional embodiments of the magnetic sensor 2100. The sensitivity of the magnetic sensor 2100 to crashes, or other detectable events, can be set to a desired level by adjusting gain and/or threshold values associated therewith. Furthermore, in addition crash sensing and safing, the above described embodiments—when incorporating a magnetic circuit 188 involving a door 78—can be used to detect the state of opening (i.e. open or closed) of the door 78, either responsive to the self inductance of the first coil 2042, or responsive to a second signal 2114 from an associated magnetic sensing element 2050/second coil 2054.
While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. It should be understood, that any reference herein to the term “or” is intended to mean an “inclusive or” or what is also known as a “logical OR”, wherein the expression “A or B” is true if either A or B is true, or if both A and B are true. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof.
Claims
1. A magnetic crash sensor, comprising:
- a. at least one coil in magnetic communication with at least a portion of a vehicle, wherein at least one of said portion of said vehicle and a location of said at least one coil is susceptible to deformation responsive to a crash;
- b. a signal source operatively associated with said at least one coil, wherein said signal source provides for generating a first time-varying signal, and said first time-varying signal is operatively coupled to said at least one coil so as to cause said at least one coil to generate a magnetic field; and
- c. at least one circuit, wherein said at least one circuit comprises at least one sense resistor in series with said at least one coil, said current through said at least one coil and through said at least one sense resistor is responsive to said first time-varying signal, said first time-varying signal comprises a time-varying voltage, said current through said at least one coil and through said at least one sense resistor is also responsive to a magnetic condition of said at least one coil, and said magnetic condition is responsive to said magnetic communication of said at least one coil with said portion of said vehicle, and said at least one circuit generates a second signal responsive to a voltage across said at least one sense resistor.
2. A magnetic crash sensor as recited in claim 1, wherein said at least one coil comprises a plurality of coil elements, wherein said plurality of coil elements are electrically interconnected in series with one another, and said plurality of coil elements are proximate to and are adapted to span a substantial region of a body or structural element of said vehicle, wherein said body or structural element of said vehicle is susceptible to deformation responsive to a crash.
3. A magnetic crash sensor as recited in claim 2, wherein said plurality of coil elements are operatively coupled to a substrate.
4. A magnetic crash sensor as recited in claim 1, further comprising a conductive element adapted to cooperate said at least one coil so as to provide for shaping, controlling or limiting said magnetic field generated by said at least one coil.
5. A magnetic crash sensor as recited in claim 1, wherein said at least one coil is adapted to cooperate with a gap between two portions of a body or structure of said vehicle.
6. A magnetic crash sensor as recited in claim 5, wherein said gap is in series with a magnetic circuit of said vehicle.
7. A magnetic crash sensor as recited in claim 5, wherein at least one axis of a corresponding said at least one coil is oriented substantially perpendicular to a surface bounding said gap.
8. A magnetic crash sensor as recited in claim 5, wherein at least one axis of a corresponding said at least one coil is oriented substantially parallel to a surface bounding said gap.
9. A magnetic crash sensor as recited in claim 5, wherein said at least one coil is bonded to a surface bounding said gap.
10. A magnetic crash sensor as recited in claim 1, wherein said at least one coil comprises a ferromagnetic core.
11. A magnetic crash sensor as recited in claim 1, wherein said at least one coil is operatively coupled to said body or structure of said vehicle with a fastener through a central portion of said at least one coil.
12. A magnetic crash sensor as recited in claim 1, wherein said at least one coil is located between an outward facing surface of said body or structure of said vehicle and an inward facing surface of a proximate door of said vehicle.
13. A magnetic crash sensor as recited in claim 1, wherein at least one said coil comprises a toroidal helical coil.
14. A magnetic crash sensor as recited in claim 1, wherein said signal source comprises an oscillator.
15. A magnetic crash sensor as recited in claim 14, wherein said first time-varying signal comprises a sinusoidal signal.
16. A magnetic crash sensor as recited in claim 1, wherein said at least one circuit comprises at least one demodulator adapted to generate a third signal responsive to said second signal, and said third signal is responsive to a component of said second signal that is in-phase with said first time-varying signal.
17. A magnetic crash sensor as recited in claim 1, wherein said at least one circuit comprises at least one demodulator adapted to generate third and fourth signals responsive to said second signal, said third signal is responsive to a component of said second signal that is in-phase with said first time-varying signal, and said fourth signal is responsive to a component of said second signal that is in quadrature-phase with respect to said first time-varying signal.
18. A magnetic crash sensor as recited in claim 17, wherein said third and fourth signals are responsive to, or provide a measure of, a self-impedance of said at least one coil.
19. A magnetic crash sensor as recited in claim 1, further comprising a safety restraint system, wherein an actuation of said safety restraint system is controlled responsive to said second signal.
20. A magnetic crash sensor as recited in claim 16, wherein an actuation of said safety restraint system is controlled responsive to at least said third signal.
21. A magnetic crash sensor as recited in claim 17, wherein an actuation of said safety restraint system is controlled responsive to at least said third and fourth signals.
22. A magnetic crash sensor as recited in claim 1, wherein said at least one circuit comprises at least one of a discrete electrical component, an analog circuit element, a logic circuit element, a logic array, and a computer processor.
Type: Application
Filed: Jun 11, 2009
Publication Date: Dec 24, 2009
Patent Grant number: 8180585
Applicant: TK HOLDINGS, INC. (Farmington Hills, MI)
Inventors: Leonard S. CECH (Brighton, MI), William Todd WATSON (Belleville, MI), James D. BAAL (Novi, MI), Scott E. BAUER (Holly, MI), Timothy J. BOMYA (Westland, MI), Richard W. SMITH (Dearborn, MI)
Application Number: 12/483,236
International Classification: G06F 19/00 (20060101);